| Document and Entity Information | Mar. 31, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | GALECTIN THERAPEUTICS INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001133416 |
| Document Type | 8-K |
| Document Period End Date | Mar. 31, 2021 |
| Entity Incorporation State Country Code | NV |
| Entity File Number | 001-31791 |
| Entity Tax Identification Number | 04-3562325 |
| Entity Address, Address Line One | 4960 PEACHTREE INDUSTRIAL BOULEVARD |
| Entity Address, Address Line Two | STE 240 |
| Entity Address, City or Town | NORCROSS |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30071 |
| City Area Code | (678) |
| Local Phone Number | 620-3186 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock $0.001par value per share |
| Trading Symbol | GALT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
