| Document And Entity Information | Jul. 22, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jul. 21, 2024 |
| Entity Registrant Name | MEI Pharma, Inc. |
| Entity Central Index Key | 0001262104 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-41827 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 51-0407811 |
| Entity Address, Address Line One | 11455 El Camino Real, Suite 250 |
| Entity Address, City or Town | San Diego |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92130 |
| City Area Code | 858 |
| Local Phone Number | 369-7100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.00000002 par value |
| Trading Symbol | MEIP |
| Security Exchange Name | NASDAQ |
