Modern HIV tests are extremely accurate, but precise accuracy all depends on how long after HIV exposure you get tested and what kind of test you’re using. Generally, HIV tests after the three-month window are more than 99.97% accurate. However, no HIV tests can tell if you’re infected if you get tested immediately after exposure.
The three main tests for HIV include:
- Nucleic acid tests, which involve drawing the blood to see if the virus is present. It can be done in a clinic or doctor’s office and predicts HIV infection about one to four weeks after exposure.
- Antigen/antibody test, which tests the blood to see if there are any antibodies (substances produced by your immune system as a reaction to HIV) or antigens (substances produced by HIV that stimulate your immune system) in your blood. These tests can be done at a doctor’s office or clinic and offer rapid results. Vein blood tests are more accurate than finger prick blood tests and can detect HIV three to five weeks after exposure.
- Antibody test, which just looks for antibodies in your blood or saliva. These tests are common at clinics, but there are also home versions you can use to test yourself. These can start to predict HIV infection about three weeks to three months after exposure.
In rare cases a result can be incorrect or uncertain. Test results could indicate that you are infected with HIV when you are not (which is called a “false positive”) or they could fail to detect HIV when you really are infected (called a “false negative”). The HIV test used by Nurx was studied in more than 800 people collecting their own blood samples, and 100% of the time individuals were correctly categorized as positive or negative.
In some cases, an HIV test may not be able to tell whether you are infected at all (called an “indeterminate” result). In these cases, we recommend repeating the test or using a different test. If you recently have been infected with HIV, it may take some time before a test will detect the infection. For this reason, we may recommend that you repeat the test after a short period of time (days to weeks).