| Document and Entity Information | Nov. 15, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001576885 |
| Document Type | 8-K |
| Document Period End Date | Nov. 15, 2021 |
| Entity Registrant Name | Acumen Pharmaceuticals, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-40551 |
| Entity Tax Identification Number | 36-4108129 |
| Entity Address, Address Line One | 427 Park St. |
| Entity Address, City or Town | Charlottesville |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 22902 |
| City Area Code | (434) |
| Local Phone Number | 297-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.0001 par value |
| Trading Symbol | ABOS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
