The ‘window period’ is the time period between potential exposure to HIV e.g. sex without a condom, and the point when the test will give you an accurate result.
Tests done too early may not be accurate.
The HIV blood test is unlikely to detect HIV if you have contracted it in the last 4 weeks. However, if you are worried about a specific risk within the last 4 weeks, you should still do the test, but we recommend that you purchase another test to do 4 weeks after the last exposure.