Document and Entity Information - shares	6 Months Ended
	Jan. 31, 2019	Apr. 01, 2019
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 Emerging Growth Company	false
Entity Ex Transition Period	false
Trading Symbol	GNBT
Document Type	10-Q/A
Amendment Flag	true
Amendment description	On March 26, 2019, the Audit Committee of the Board of Directors (the “Audit Committee”) of Generex Biotechnology Corporation (the “Company”), after considering the recommendations of management and consulting with MNP, LLP, the Company’s independent registered public accounting firm, concluded that our unaudited condensed interim consolidated financial statements included in fathe quarterly reports on Form 10-Q for the period ended January 31, 2019 should not be relied upon since the auditors had not completed their interim review and their comments were not incorporated into the documents as filed primarily related the recent acquisitions of the assets and operations Veneto Holdings LLC, valuation and purchase price allocations of Regentys Corporation and Olaregen Therapeutix Inc. , and related notes and disclosures.
Document Period End Date	Jan. 31, 2019
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2019
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		60,362,143