SCHEDULE 13G

Amendment No. 1
USANA Health Sciences Inc
Common Stock
Cusip #90328M107


Cusip #90328M107
Item 1:	Reporting Person - FMR LLC
Item 4:	Delaware
Item 5:	1,638,900
Item 6:	0
Item 7:	1,638,900
Item 8:	0
Item 9:	1,638,900
Item 11:	10.053%
Item 12:	    HC


Cusip #90328M107
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	1,638,900
Item 8:	0
Item 9:	1,638,900
Item 11:	10.053%
Item 12:	IN




	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



Item 1(a).	Name of Issuer:

		USANA Health Sciences Inc

Item 1(b).	Name of Issuer's Principal Executive Offices:

		3838 West Parkway Blvd
		Salt Lake City, UT  84120-6336


Item 2(a).	Name of Person Filing:

		FMR LLC

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston,
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock

Item 2(e).	CUSIP Number:

		90328M107

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR LLC, is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	1,638,900

	(b)	Percent of Class:	10.053%

	(c)	Number of shares as to which such
person has:

	(i)	sole power to vote or to direct
the vote:	1,638,900

	(ii)	shared power to vote or to
direct the vote:	0

	(iii)	sole power to dispose or to
direct the disposition of:	1,638,900

	(iv)	shared power to dispose or to
direct the disposition of:	0



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

	Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the
sale of, the Common Stock of USANA Health Sciences Inc.
The interest of one person, Fidelity Northstar Fund, an open-
end, Canadian mutual fund trust formed by declaration of trust
on October 8, 2002, in the Common Stock of USANA Health
Sciences Inc, amounted to 1,638,900 shares or 10.053% of the
total outstanding Common Stock at August 31, 2008.

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

	See attached Exhibit A.

Item 8.	Identification and Classification of Members of
the Group.

	Not applicable.  See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in the
ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in any
transaction having such purpose or effect.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement
is true, complete and correct.

September 09, 2008
Date

 /s/ Scott C. Goebel
Signature

Scott C. Goebel
Duly authorized under Power of Attorney
effective as of June 1, 2008 by and on behalf of FMR LLC
and its direct and indirect  subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



		Pyramis Global Advisors, LLC ("PGALLC"),
53 State Street, Boston, Massachusetts, 02109, an indirect
wholly-owned subsidiary of FMR LLC and an investment
adviser registered under Section 203 of the Investment
Advisers Act of 1940, is the beneficial owner of 1,638,900
shares or 10.053% of the outstanding Common Stock of
USANA Health Sciences Inc as a result of its serving as
investment adviser to institutional accounts, non-U.S. mutual
funds, or investment companies registered under Section 8 of
the Investment Company Act of 1940 owning such shares.

		The ownership of one Canadian mutual fund,
Fidelity Northstar Fund, amounted to 1,638,900 shares or
10.053% of the Common Stock outstanding. Fidelity Northstar
Fund has its principal business office at 483 Bay Street, Suite
200, Toronto, Ontario M5G 2N7, Canada.

	Edward C. Johnson 3d and FMR LLC, through its
control of PGALLC, each has sole dispositive power over
1,638,900 shares and sole power to vote or to direct the voting
of 1,638,900 shares of Common Stock owned by the
institutional accounts or funds advised by PGALLC as
reported above.

	Members of the family of Edward C. Johnson 3d,
Chairman of FMR LLC, are the predominant owners, directly
or through trusts, of Series B voting common shares of FMR
LLC, representing 49% of the voting power of FMR LLC.
The Johnson family group and all other Series B shareholders
have entered into a shareholders' voting agreement under
which all Series B voting common shares will be voted in
accordance with the majority vote of Series B voting common
shares.  Accordingly, through their ownership of voting
common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed,
under the Investment Company Act of 1940, to form a
controlling group with respect to FMR LLC.



	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on September 10, 2008,
agree and consent to the joint filing on their behalf of this
Schedule 13G in connection with their beneficial ownership of
the Common Stock of USANA Health Sciences Inc at August
31, 2008.

	FMR LLC

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of FMR LLC and its direct
and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of Edward C. Johnson 3d

	Fidelity Northstar Fund

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Secretary

	Pyramis Global Advisors, LLC

	By /s/Claire S. Walpole
	Claire S. Walpole
	Duly authorized under Power of Attorney
	dated August 8, 2007, by William E. Dailey
	Senior Vice President
	and Chief Administrative Officer
	Duly authorized under Board of
	Directors resolution dated
	September 26, 2005.