"I was almost dying," he told The Anadolu Agency in an interview.
But Sibanda started having problems accessing the drug towards the end of the 2014.
"I would go to Parirenyatwa [a major referral hospital in Harare] for my supply, only to be told to go and buy the drugs at a private pharmacy, where it cost nearly $40," he complained.
"I am not employed. This meant I was now at risk of defaulting treatment," Sibanda fumed.
Zimbabwean hospitals are facing a shortage of ARVs, placing the lives of hundreds of thousands of people living with the virus at risk.
"Zimbabweans living with HIV/AIDS face an adherence problem due to the ARVs shortage affecting the country at the moment," Gumiso Bonzo, director of the Zimbabwean Mighty Women of Hope Support Organization, a local NGO, told AA.
But Owen Mugurungi, AIDS and Tuberculosis unit director at the Zimbabwean Health Ministry, said he was not aware of any shortages at Harare hospital.
"We are not aware of that issue, so we will wait for the report to come to us; the country has enough drugs," he said at an HIV/AIDS forum in December.
Zimbabwe has one of the highest rates of HIV/AIDS in the world, with nearly 15 percent of the population said to be HIV-positive.
Although there are said to be nearly 1.6 million adults living with HIV, only half are estimated to be on ARVs offered by donors like the Global Fund.
The Fund – a partnership between governments, civil society, the private sector and people devoted to ending AIDS – raises and invests nearly $4 billion a year to support programs run by local experts in more than 140 countries.
Other donors include the U.S. President's Emergency Plan for AIDS Relief, an initiative to help save the lives of those suffering from HIV/AIDS around the world.
Stanley Takaona, vice president of the Zimbabwe HIV and Aids Activist Union, accused the government of endangering the lives of patients.
He said the shortage of certain ARVs was so severe that adults in some cases were being given drugs intended for infants.
"We have received those reports from some of our members and are looking into the matter," he told AA.
Malon Tom, 22, told AA that he had been given children's syrup – instead of the needed ARV – at one opportunistic infection clinic at the Parirenyatwa Hospital in December.
Takaona fears some patients could be receiving the wrong treatment, or expired drugs.
"We are afraid that some of the people taking the life-saving drug could be receiving the wrong drugs or expired drugs as the shortage of some ARVs becomes apparent," he said.
The World Health Organization recommends due diligence if an HIV/AIDS patient is to switch from one drug to another in order to avoid a mutation of the virus.
"A lot of people are being turned away from government hospitals without having received adequate supplies, forcing them to buy the drugs on the black market," said Takaona.
A nurse at a major Harare hospital said ARVs were being sold for cash in some cases by underpaid doctors and nurses.
"There are times when the drugs are in short supply, not because they are not available at the hospital, but because hospital staff steal and sell them on the black market," she told AA.
The allegation could not be independently verified.
On the black market, the live-saving drugs are sold for around $25.
Irene Siziba, a 19-year girl, says she has bought ARVs on the black market in Harare on several occasions.
"My older brother had to buy ARVs on the black market on my behalf, as I could not find them at Harare's Parirenyatwa Hospital," she told AA.