Cover Page - shares	3 Months Ended
	Sep. 30, 2021	Nov. 08, 2021
Cover [Abstract]
Document Type	10-Q/A
Amendment Flag	true
Amendment Description	MEI Pharma, Inc. (the "Company") hereby amends its Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, filed with the Securities and Exchange Commission (the "SEC") on November 10, 2021 (the "Original Quarterly Report"), as set forth in this Amendment No. 1 on Form 10-Q/A (the "Form 10-Q/A" or "Amended Quarterly Report"), to restate its financial statements and related disclosures as of and for the quarters ended September 30, 2021 and 2020.
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity File Number	000-50484
Trading Symbol	MEIP
Entity Registrant Name	MEI Pharma, Inc.
Entity Tax Identification Number	51-0407811
Entity Central Index Key	0001262104
Current Fiscal Year End Date	--06-30
Entity Filer Category	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
City Area Code	858
Local Phone Number	369-7100
Entity Small Business	true
Title of 12(b) Security	Common Stock, $0.00000002 par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	11455 El Camino Real
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92130
Entity Interactive Data Current	Yes
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		112,721,212