| Cover | Feb. 27, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 27, 2024 |
| Entity File Number | 001-38898 |
| Entity Registrant Name | APPLIED THERAPEUTICS, INC. |
| Entity Central Index Key | 0001697532 |
| Entity Tax Identification Number | 81-3405262 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 545 Fifth Avenue |
| Entity Address, Address Line Two | Suite 1400 |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10017 |
| City Area Code | 212 |
| Local Phone Number | 220-9226 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | APLT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | true |
