Document and Entity Information - USD ($)	12 Months Ended
	Jul. 31, 2017	Sep. 29, 2017
Document And Entity Information
Entity Registrant Name	GENEREX BIOTECHNOLOGY CORP
Entity Central Index Key	0001059784
Document Type	10-K
Document Period End Date	Jul. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--07-31
Is Entity a Well-known Seasoned Issuer?	No
Is Entity a Voluntary Filer?	No
Is Entity's Reporting Status Current?	Yes
Entity Filer Category	Smaller Reporting Company
Entity Public Float	$ 5,300,000
Entity Common Stock, Shares Outstanding		1,065,093
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2017