Document and Entity Information - USD ($)	12 Months Ended
	Jul. 31, 2018	Oct. 26, 2018
Document And Entity Information
Entity Registrant Name	GENEREX BIOTECHNOLOGY CORP
Entity Central Index Key	0001059784
Current Fiscal Year End Date	--07-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Shell Company	false
Entity Emerging Growth Company	false
Trading Symbol	GNBT
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jul. 31, 2018
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2018
Entity Well-Known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		1,065,093
Entity Public Float	$ 2,200,000