Exhibit 24

                               POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              VENTURE INVESTORS EARLY STAGE FUND IV LP

                              By:         /s/ John Neis
                                          --------------------------------------

                              Print Name: John Neis
                                          --------------------------------------

                              Title:      Managing Director
                                          --------------------------------------

                               POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              VENTURE INVESTORS LLC

                              By:         /s/ John Neis
                                          -------------------------------------
                              Print Name: John Neis
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------

                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.


                              VIESF IV GP LLC


                              By:         /s/ John Neis
                                          -------------------------------------
                              Print Name: John Neis
                                          -------------------------------------
                              Title:      Member
                                          -------------------------------------

                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.


                              By:         /s/ John Neis
                                          -------------------------------------
                              Print Name: John Neis
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------

                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              By:         /s/ Paul M. Weiss, Ph.D.
                                          -------------------------------------
                              Print Name: Paul M. Weiss, Ph.D.
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------

                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              By:         /s/ Scott Button
                                          -------------------------------------
                              Print Name: Scott Button
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------

                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              By:         /s/ George Arida
                                          -------------------------------------
                              Print Name: George Arida
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------


                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              By:         /s/ James R. Adox
                                          -------------------------------------
                              Print Name: James R. Adox
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------


                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.


                              By:         /s/ Loren G. Peterson
                                          -------------------------------------
                              Print Name: Loren G. Peterson
                                          -------------------------------------
                              Title:      Managing Director
                                          -------------------------------------


                                POWER OF ATTORNEY

        Know all by these present, that the undersigned hereby constitutes and
appoints each of John P. Butler, Jason A. Amello and Nicole R. Hadas, signing
singly, as the undersigned's true and lawful attorney-in-fact to:

        (1)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as an officer and/or director or
                shareholder of Akebia Therapeutics, Inc. (the "Company"), Forms
                3, 4 and 5 in accordance with Section 16(a) of the Securities
                Exchange Act of 1934, as amended (the "Act"), and the rules
                thereunder;

        (2)     do and perform any and all acts for and on behalf of the
                undersigned which may be necessary or desirable to complete and
                execute any such Form 3, 4 or 5 and timely file such form with
                the United States Securities and Exchange Commission and any
                stock exchange or similar authority; and

        (3)     take any other action of any type whatsoever in connection with
                the foregoing which, in the opinion of such attorney-in-fact,
                may be of benefit to, in the best interest of, or legally
                required by, the undersigned, it being understood that the
                documents executed by such attorney-in-fact on behalf of the
                undersigned pursuant to this Power of Attorney shall be in such
                form and shall contain such terms and conditions as such
                attorney-in-fact may approve in such attorney-in-fact's
                discretion.

        The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all the acts such attorney-in-fact shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that each of the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, is not assuming any of the undersigned's responsibilities to comply
with Section 16 of the Act.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to each
of the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of March 17, 2014.

                              VENTURE INVESTORS SOUTHEAST LLC

                              By:         /s/ Roger H. Ganser
                                          -------------------------------------
                              Print Name: Roger H. Ganser
                                          -------------------------------------
                              Title:      Managing Partner
                                          -------------------------------------