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HIV Test Window Period: How Soon Can a Test Detect HIV?

By Richard D. Porter, Patient Advocate Updated

Quick answer

The window period is the time between an HIV exposure and when a test can detect HIV. The CDC says a NAT can usually detect HIV 10 to 33 days after exposure, a lab antigen/antibody test with blood from a vein 18 to 45 days, a finger-stick rapid antigen/antibody test 18 to 90 days, and an antibody test 23 to 90 days. If you test negative before the window ends, test again after it. If your possible exposure was in the last 72 hours, don't wait for a test window: go to urgent care or an ER now and ask about PEP.

The test you need

HIV: NAT (tests for the virus)Reliable by day 33

HIV: Antigen/antibody lab testReliable by day 45

HIV: Antibody test or self-testReliable by day 90

Too earlyMay detect; retest if negativeReliable

Counted from your most recent exposure. Source: CDC. Work out your own dates

Test
HIV antigen/antibody lab test or NAT, depending on how soon after exposure you test
Sample
Blood from a vein (lab antigen/antibody test, NAT), a finger stick (rapid tests), or oral fluid (some antibody and self-tests)
When
NAT: 10 to 33 days. Lab antigen/antibody test: 18 to 45 days. Finger-stick rapid antigen/antibody test: 18 to 90 days. Antibody test: 23 to 90 days (all per the CDC).

“How long should I wait to test?” is the right question, and the answer isn’t one number. It depends on which type of test you take. This page gives the CDC’s ranges and what to do with them.

What if I was exposed in the last 3 days?

This comes first. The CDC says PEP (post-exposure prophylaxis) is medicine that prevents HIV after a possible exposure, that it must be started within 72 hours (3 days) of a recent possible exposure, and that it’s for emergency situations. Go to urgent care or an emergency room now, or contact a health care provider right away, and ask about PEP. Testing is not the first step, and you don’t need to wait for a window period to pass before seeking care.

What is the HIV window period?

The CDC defines it as the time between a potential HIV exposure and when a test can detect HIV in the body. A test taken inside that window can come back negative even if HIV is present, because there isn’t yet enough of the virus or enough antibodies for that test to pick up.

How long after exposure can each test detect HIV?

These are the CDC’s ranges, counted from the exposure:

  • Nucleic acid test (NAT): usually 10 to 33 days. It looks for the virus itself.
  • Antigen/antibody lab test (blood from a vein): usually 18 to 45 days.
  • Rapid antigen/antibody test (finger stick): usually 18 to 90 days.
  • Antibody test: usually 23 to 90 days. Most rapid tests and self-tests are antibody tests, according to HIV.gov.

Some sellers describe an antigen/antibody lab test as “fourth generation” and quote a single shorter date for it. Use the CDC ranges above as your guide, and treat any single “you’re clear by day X” figure from a seller with caution.

Why is a rapid test listed with a longer window?

Because rapid is about speed of result, not early detection. The finger-stick rapid antigen/antibody test is listed at 18 to 90 days, while the lab version is listed at 18 to 45 days. If you need the earliest reliable answer, ask for a lab antigen/antibody test or a NAT rather than a rapid test.

What about home tests?

The FDA says the window period for the OraQuick In-Home HIV Test is about three months, and that a negative result doesn’t mean someone is definitely not infected, particularly when exposure may have been within the previous three months. The CDC lists antibody tests at 23 to 90 days. A home test is best used at around the 90-day mark.

When should I test again after a negative result?

The CDC says: if you get an HIV test after a potential exposure and the result is negative, get tested again after the window period for the test you took. So the question is which test you took:

  • Took a NAT at 14 days and it was negative? The NAT window runs to 33 days, so a later test is still needed.
  • Took a lab antigen/antibody test at 30 days? The range runs to 45 days.
  • Took a rapid or home antibody test at 6 weeks? The range runs to 90 days.

If you test again after the window period, have no possible exposure during that time, and the result is negative, the CDC says you do not have HIV.

What if I need an answer sooner?

Two things can help. First, if the exposure was within 72 hours, PEP is the priority. Second, a NAT has the shortest window, and the CDC says it should be considered for people who have had a recent or possible exposure and have early symptoms of HIV but tested negative on an antibody or antigen/antibody test. A clinician can advise on whether it fits your situation. Remember that even a NAT result before day 33 may need a later retest.

What if the risk is ongoing?

The CDC’s ranges are counted from a possible exposure. For ongoing risk, the CDC advises clinicians to retest people for HIV as long as they have ongoing risk factors, and to screen them at least annually. The CDC also says everyone ages 13 to 64 should be tested for HIV at least once. A clinician can help you set a schedule.

Get care now if

  • You may have been exposed to HIV in the last 72 hours. Go to urgent care or an emergency room now and ask about PEP. Don't wait for the window period.
  • You tested positive on a rapid or home test. You need a follow-up test from a healthcare provider to confirm.
  • You are pregnant and think you may have been exposed. Contact a clinician now.

Call 911 for a medical emergency. Otherwise, an urgent care clinic, sexual health clinic or your doctor can see you.

When to test

  1. Within 72 hours of a possible exposureGo to urgent care or an emergency room now and ask about PEP. The CDC says PEP must be started within 72 hours. This comes before any test.
  2. 10 to 33 days after exposureA NAT can usually detect HIV in this window. Ask a clinician or lab about ordering one. A negative this early may need a later retest.
  3. 18 to 45 days after exposureA lab antigen/antibody test with blood from a vein can usually detect HIV in this range.
  4. 90 days after exposureBy day 90, antibody tests, including finger-stick rapid tests and home self-tests, can usually detect HIV. The CDC says to test again after the window period for the test you took.

Common questions

Can an HIV test detect HIV at 2 weeks?

Possibly, with the right test. The CDC says a NAT can usually detect HIV 10 to 33 days after exposure, so at 14 days it may. The CDC lists antigen/antibody tests from 18 days and antibody tests from 23 days, so they aren't expected to detect HIV that early. A negative at 2 weeks isn't the last word.

Is 4 or 6 weeks enough?

It depends on the test. The CDC range for a lab antigen/antibody test runs to 45 days, which is about 6.5 weeks, and for antibody tests to 90 days. A negative before the end of the range for your test should be repeated.

Does a rapid test detect HIV sooner?

No. Rapid describes how fast you get the result. A finger-stick rapid antigen/antibody test is listed by the CDC at 18 to 90 days, compared with 18 to 45 days for the lab version.

What is a fourth-generation HIV test?

Some sellers, such as STDCheck, use that name for an antigen/antibody test. The CDC describes it as looking for both HIV antibodies and antigens, with a window of 18 to 45 days for blood drawn from a vein.

Next: HIV antigen/antibody lab test or NAT, depending on how soon after exposure you test.

Blood from a vein (lab antigen/antibody test, NAT), a finger stick (rapid tests), or oral fluid (some antibody and self-tests). NAT: 10 to 33 days. Lab antigen/antibody test: 18 to 45 days. Finger-stick rapid antigen/antibody test: 18 to 90 days. Antibody test: 23 to 90 days (all per the CDC).

Read next

Sources

This guide is general information written by a patient advocate using public health sources. It is not a diagnosis. Only a clinician or a lab test can tell you whether you have an infection. Read how we write and check our guides.