| Document And Entity Information | Apr. 01, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 01, 2024 |
| Entity Registrant Name | Fractyl Health, Inc. |
| Entity Central Index Key | 0001572616 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-41942 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 27-3553477 |
| Entity Address, Address Line One | 3 Van de Graaff Drive |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | Burlington |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01803 |
| City Area Code | (781) |
| Local Phone Number | 902-8800 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common Stock, $0.00001 par value per share |
| Trading Symbol | GUTS |
| Security Exchange Name | NASDAQ |
