Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Mar. 17, 2025	Jun. 30, 2024
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
Document Transition Report	false
Entity File Number	001-37809
Entity Registrant Name	METAVIA INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-2389984
Entity Address, Address Line One	545 Concord Avenue, Suite 210
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	857
Local Phone Number	702-9600
Title of 12(b) Security	Common stock, $0.001 par value
Trading Symbol	MTVA
Security Exchange Name	NASDAQ
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 13.8
Entity Common Stock, Shares Outstanding		8,654,869
Auditor Firm ID	243
Auditor Name	BDO USA, P.C.
Auditor Location	Boston Massachusetts
Entity Central Index Key	0001638287
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Amendment Flag	false