The window period
After HIV enters the body, it takes time before a test can pick it up. That gap is the window period. During it, a person can have HIV and still test negative. Each type of test looks for something different, so each has its own window.
| Test | Detects HIV from | Negative is conclusive from |
|---|---|---|
| Nucleic acid test (NAT / RNA) | 10 days | 33 days |
| Antigen/antibody lab test (4th gen, blood from a vein) | 18 days | 45 days |
| Rapid antigen/antibody test (finger-prick) | 18 days | 90 days |
| Antibody test (most rapid tests and home self-tests) | 23 days | 90 days |
Nucleic acid test (NAT)
Looks for the virus's genetic material in blood. It's the earliest test, but it's expensive and not offered everywhere. It's mainly used when someone has had a recent high-risk exposure or has symptoms of early infection.
Antigen/antibody test (4th generation)
The standard test in most clinics and labs. It detects both HIV antibodies and p24, a protein from the virus that appears before antibodies do. Done on blood from a vein, it's conclusive at 45 days. The finger-prick rapid version needs up to 90 days.
Antibody test
Detects only the antibodies your body makes in response to HIV, which take longer to appear. Most rapid tests and home self-tests, including oral-swab tests, are antibody tests and are conclusive from 90 days.
A testing timeline
- Days 0 to 3: Too early for any test. If the risk was significant, this is the time to get PEP.
- Days 10 to 33: A NAT can detect most infections and becomes conclusive at day 33.
- Days 18 to 45: A lab antigen/antibody test detects most infections; a negative result at 45 days is conclusive.
- Day 90 onward: Every test, including home self-tests, gives a conclusive result.
Testing early can still be useful, especially if you're anxious, but plan a follow-up test once the window has closed. If you took PEP, follow your clinician's schedule; CDC recommends tests about 4 to 6 weeks and 12 weeks after the exposure.
Symptoms are not a test
Some people get a flu-like illness 2 to 4 weeks after getting HIV, with fever, rash, sore throat, swollen glands or mouth ulcers. Many people have no symptoms at all, and all of these symptoms have far more common causes. If you have them after a possible exposure, see a clinician and ask for a test that can detect early infection.
Where to get tested
- Sexual health and STI clinics, often free and confidential
- Your doctor or a community health center
- Pharmacies and community organizations offering rapid tests
- Home self-test kits from pharmacies or online
In the US, gettested.cdc.gov lists free testing near you. Elsewhere, national health services and sexual health charities usually run similar finders.
After your result
Negative after the window period: you don't have HIV from that exposure. If you're likely to be exposed again, ask about PrEP.
Negative inside the window period: reassuring, but retest once the window closes.
Positive or reactive: you'll need a follow-up lab test to confirm it. If HIV is confirmed, treatment is simple, very effective, and lets people with HIV live long, healthy lives without passing it on to sexual partners.