v3.26.1
Document and Entity Information - shares
 12 Months Ended
Dec. 31, 2025
Mar. 23, 2026
Cover [Abstract]    
Document Type 10-K  
Amendment Flag false  
Document Annual Report true  
Document Transition Report false  
Document Period End Date Dec. 31, 2025  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Entity File Number 001-42831  
Entity Registrant Name LB Pharmaceuticals Inc  
Document Fiscal Period Focus FY  
Entity Central Index Key 0001691082  
Entity Tax Identification Number 81-1854347  
Entity Incorporation, State or Country Code DE  
Entity Address, Address Line One One Pennsylvania Plaza  
Entity Address, Address Line Two Suite 1025  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10119  
City Area Code 212  
Local Phone Number 605-0300  
Title of 12(b) Security Common Stock, $0.0001 par value  
Trading Symbol LBRX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Well-known Seasoned Issuer No  
Entity Voluntary Filers Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   28,674,827
Document Financial Statement Error Correction [Flag] false  
ICFR Auditor Attestation Flag false  
Documents Incorporated by Reference [Text Block]

DOCUMENTS INCORPORATED BY REFERENCE

Part III incorporates certain information by reference from the registrant’s proxy statement for the 2026 Annual Meeting of Shareholders. Such proxy statement will be filed no later than 120 days after the close of the registrant’s fiscal year ended December 31, 2025.

  
Auditor Firm ID 243  
Auditor Name BDO USA, P.C  
Auditor Location New York  
Auditor Opinion [Text Block]

Opinion on the Financial Statements

We have audited the accompanying balance sheets of LB Pharmaceuticals Inc (the “Company”) as of December 31, 2025 and 2024, the related statements of operations, comprehensive loss, redeemable convertible preferred stock and stockholders’ equity (deficit), and cash flows for each of the years then ended, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company at December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the years then ended, in conformity with accounting principles generally accepted in the United States of America.