| Document and Entity Information | Mar. 23, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 23, 2023 |
| Entity Registrant Name | Metacrine, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39512 |
| Entity Tax Identification Number | 47-2297384 |
| Entity Address, Address Line One | 4225 Executive Square |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | San Diego |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92037 |
| City Area Code | 858 |
| Local Phone Number | 369-7800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| No Trading Symbol Flag | true |
| Security Exchange Name | NONE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Amendment Flag | false |
| Entity Central Index Key | 0001634379 |
