What testing service you should use, and which type of test, depends on when you might have been exposed to HIV. Signs of HIV infection don’t show up in the blood right away. It normally happens within four weeks of infection, but can be longer.
If you think you might have been exposed to HIV in the last 72 hours (three days), it’s possible to take post-exposure prophylaxis (PEP) to help stop an infection from happening.
If your risk was recent, then your test provider will probably advise you to take a test immediately, followed by a second one a few weeks later. The second test will pick up any infection the first one may have missed.
If your risk was in the last three months, make sure you tell the person testing you, as it may affect the type of test you’re given.
A self test is not guaranteed to pick up an infection that’s occurred in the previous three months. If you think you’ve been exposed in the last three months, you should get a test in person.
Very occasionally it can take up to three months for antibodies to appear in the blood, so an HIV negative result is only totally accurate if three months have passed between the test and the last time a risk was taken. However, a negative result four to eight weeks after taking a risk is a very good sign that HIV infection hasn’t happened.