Andy Warhol, along with his friends and "Superstars," were known for their notoriously liberal views on drugs. While there are few reliable records on whether Warhol himself was a heroin user, it is uncontested that he more than dabbled in a few drugs.^1 His friend Bob Colacello said that Warhol "flirted" with cocaine, and "even heard [Warhol] deny taking it as he was sticking it up his nose."^2 Because of Warhol's habit of denial, it is difficult to take his word at face value in sources discussing his drug uses.
Two of his most famous friends, society girl Edie Sedgwick and Lou Reed of The Velvet Underground, were confirmed heroin users. Edie Sedgewick was hospitalized multiple times for drug abuse and mental instability, and Lou Reed past away due to complications from a liver transplant (which he needed because he contracted hepatitis from sharing needles with other heroin users).^3 From Warhol's friendship wtih Sedgwick and Reed, it can be reasonably surmised that Warhol was, at the very least, tolerant of heroin usage.
Although the Factory had a reputation for being the hip hangout for drug addicts, Warhol's personal interest in drugs waned, and it is possible that his view on drug use changed. Warhol Superstar and Factory regular Jane Forth reported that he moved on from those "earlier days" of drug use (before she joined his entourage in 1969) to get down to business.^4 Indeed, Warhol and Sedgwick's falling out in late 1965 may have been escalated by her increasing substance abuse compounded with his new turn away from drugs, along with professional disagreements on their film collaborations.^5
Sources: