DEI Document - shares	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018
Entity [Abstract]
Entity Registrant Name	Menlo Therapeutics Inc.
Entity Central Index Key	0001566044
Trading Symbol	MNLO
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		23,232,184