DEI Document - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Entity [Abstract]
Entity Registrant Name	Menlo Therapeutics Inc.
Entity Central Index Key	0001566044
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		22,977,998
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes