Antiretroviral Therapy (ART) for HIV: How It Works and Side Effects
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
Antiretroviral therapy (ART) is a combination of medicines that treats HIV by stopping the virus from copying itself. It isn't a cure, but over 90% of people who take it as prescribed reach an undetectable viral load within 12 months, which means they can't pass HIV through sex. Anyone with HIV should start ART as soon as possible.
What the research says
Starting ART right away improved health: in the START trial of 4,685 adults with healthy CD4 counts, starting ART immediately cut serious AIDS events, serious non-AIDS events or death from 4.1% to 1.8% compared with waiting (Lundgren JD et al., New England Journal of Medicine, 2015) [2]
Undetectable means untransmittable: the PARTNER2 study followed 782 couples through about 76,088 acts of condomless sex while the partner with HIV had a suppressed viral load on ART and found zero HIV transmissions within couples (Rodger AJ et al., Lancet, 2019) [3]
Key takeaways
ART is a combination of HIV medicines.
It lowers viral load and protects your immune system.
Over 90% reach an undetectable viral load within a year.
Undetectable HIV can't be passed through sex.
ART is lifelong; missing doses can cause resistance.
What is antiretroviral therapy?
HIV destroys CD4 (helper T) cells. ART blocks the virus at different steps of its life cycle, which lets your body make more CD4 cells. It's also called cART or HAART. Sources: [1]
Why it's used
Starting early works better than waiting.
Lowers your viral load.
Protects your immune system.
Lowers the risk of serious infections, certain cancers and AIDS.
Prevents sexual transmission when your viral load is undetectable. Sources: [1, 3]
Starting early is more successful than waiting for CD4 counts to drop. Sources: [1, 2]
Classes of HIV medicines
Most regimens combine two to four medicines.
Class | How it works | Examples |
NRTIs | Act as decoy building blocks | Emtricitabine, tenofovir, lamivudine |
NNRTIs | Bind reverse transcriptase | Doravirine, efavirenz, rilpivirine |
Integrase inhibitors (INSTIs) | Block integrase | Bictegravir, dolutegravir, cabotegravir |
Protease inhibitors | Block protease | Darunavir, atazanavir |
Capsid inhibitors | Bind capsid proteins | Lenacapavir |
Entry inhibitors | Block attachment or fusion | Maraviroc, fostemsavir |
Most regimens combine two NRTIs with an INSTI, an NNRTI or sometimes a boosted protease inhibitor. Sources: [1]
How ART is taken
Most people take a daily pill; some take liquids.
A shot every one or two months is an option for some people with an undetectable viral load.
Your regimen depends on your viral load, CD4 count, resistance testing, other conditions and medicines, and pregnancy plans.
Regularly missing doses, such as one or more a week, can cause the virus to rebound and become resistant. Sources: [1]
Side effects
Nausea, vomiting or diarrhea.
Trouble sleeping, mood changes or depression.
Headache, dizziness or fatigue.
Rash or dry mouth.
Weight gain or high cholesterol.
Injection-site pain. Sources: [1]
Many side effects are temporary and last a few weeks, but some, like high cholesterol, can last longer. Sources: [1]
Monitoring your treatment
Viral levels usually fall within six months.
Viral load is tested before starting and every 4 to 8 weeks until undetectable.
Then it's tested every 3 to 4 months for at least two years, then every six months if it stays low.
CD4 count is checked before starting, at three months and regularly after that. Sources: [1]
Viral levels usually fall within six months, sometimes within one to two months. Sources: [1]
Outlook
Undetectable means fewer than 20 copies of HIV per milliliter of blood. People with a consistently undetectable viral load can live as long as people without HIV. Without treatment, life expectancy is eight to 10 years. Stopping ART lets hidden virus become active again. Sources: [1]
When to call your provider
Contact your provider if you have trouble taking your medicines as prescribed or if side effects are hard to tolerate. They can adjust your medicines or help with scheduling. Sources: [1]
Conclusion
ART lets people with HIV live long, healthy lives and prevents sexual transmission. Taking it every day and keeping up with blood tests are the keys to success.
Keep learning: read about HIV and AIDS and post-exposure prophylaxis (PEP).
Frequently asked questions
What is antiretroviral therapy?
A combination of medicines that treats HIV.
Does ART cure HIV?
No, but it keeps the virus under control.
When should I start ART?
As soon as possible after diagnosis.
How is ART taken?
Usually as a daily pill; some people get a shot every one or two months.
How long until my viral load is undetectable?
Over 90% reach undetectable levels within 12 months.
Can I pass HIV if I'm undetectable?
No, not through sex.
What happens if I miss doses?
The virus can rebound and become resistant.
What are the side effects?
Nausea, headache, trouble sleeping and others, often temporary.
Will I take ART for life?
Yes.
How long can people on ART live?
As long as people without HIV when the viral load stays undetectable.
Related Reading
Protease Inhibitors: Types, How They Work and Side Effects explains protease inhibitor medicines.
HIV/AIDS: Symptoms, Causes, and How It Is Diagnosed and Treated an overview of HIV.
HIV Viral Load: Test, Normal Range, Results and What They Mean the test that tracks treatment.
CD4 Count: Normal Range, What a Low CD4 Count Means and How Often It's Checked measuring immune health.
HIV Test: Types, Window Periods, How It Works and Results how HIV is diagnosed.
Post-Exposure Prophylaxis (PEP): How It Works and When to Start medicine to prevent HIV after exposure.
References
Cleveland Clinic. Antiretroviral Therapy (ART): How It Works & Side Effects. Cleveland Clinic. Last updated September 18, 2023. https://my.clevelandclinic.org/health/treatments/antiretroviral-therapy
Lundgren JD, Babiker AG, Gordin F, et al. Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med. 2015;373(9):795-807. PMID 26192873. https://doi.org/10.1056/NEJMoa1506816
Rodger AJ, Cambiano V, Bruun T, et al. Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study. Lancet. 2019;393(10189):2428-2438. PMID 31056293. https://doi.org/10.1016/S0140-6736(19)30418-0
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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