HIV Test: When to Test, Types & What Results Mean

An HIV test is conducted to detect the presence of the virus in the body and should be taken at least 30 days after a potential exposure. This includes situations like unprotected sexual contact or direct exposure to the blood or bodily fluids of someone living with HIV.

The testing process is straightforward and typically involves a blood sample, though oral fluid (saliva) can also be used for certain screenings. Modern tests look for HIV-1 and HIV-2 antibodies, antigens, or the virus's genetic material to provide accurate results.

Depending on your results, a healthcare provider may order supplemental tests to confirm the diagnosis or measure the viral load. Early detection allows for the prompt start of antiretroviral therapy, which is essential for preventing the progression to AIDS.

When to get tested

You should wait at least one month after a potential exposure before taking an HIV test. This 30-day window, known as the window period, is the time it takes for the virus to become detectable by most standard screening methods.

Testing before the 30-day window period ends increases the risk of a false-negative result. If you receive a negative result but the exposure occurred recently, it is highly recommended to retest once the full window period has passed.

While 30 days is the standard guideline, the window period can vary based on an individual's immune system. In some cases, the virus or immune response may be detectable slightly earlier if the viral load in the bloodstream rises quickly.

Types of HIV tests and window periods

Different testing methods have varying window periods, some of which can detect the virus sooner than 30 days. The most common options include:

• Rapid antigen/antibody test: This test uses a finger-stick blood sample and can typically detect HIV 18 to 90 days after exposure. It is also referred to as the rapid HIV test. 

• 4th generation ELISA (antigen/antibody) test: This laboratory-based blood test is highly sensitive and can usually detect the virus 18 to 45 days after exposure.

• Nucleic acid test (NAT): Also known as a molecular test, this lab test looks for the virus's RNA and can detect HIV as early as 10 to 33 days after exposure.

If a healthcare provider orders a molecular test for diagnostic purposes, the third week after exposure is often the ideal time for collection, as viral concentrations in the blood are usually at their peak.

Once the initial infection phase passes, the virus primarily resides within the cells, making it harder to find with molecular tests. At that stage, antibody-based testing becomes the preferred method.

Understanding your results

Your HIV test results should always be reviewed with a healthcare professional. They will interpret the findings based on the specific test used, the timing of your exposure, and your personal health history.

HIV blood tests

A formal blood test measures both the presence of the virus and its concentration in the bloodstream to determine the stage of infection. The ELISA (Enzyme-Linked Immunosorbent Assay) method is the most frequent laboratory technique used for this purpose.

The possible results for an ELISA test include:

• Greater than 5.00 (positive or reactive): This indicates that the person has been infected with the HIV virus.

• Between 1.00 and 5.00 (indeterminate): This result is inconclusive, often because the sample was unclear. This can sometimes occur due to recent vaccinations or pregnancy.

• Less than 1.00 (negative or non-reactive): This means no evidence of an HIV infection was found.

If a test returns a positive result, laboratories automatically perform confirmatory testing, such as a Western Blot or Immunoblot, to ensure the diagnosis is 100% accurate before it is finalized.

Some lab reports include a specific numerical value alongside the reactive or non-reactive status. While interesting for medical tracking, the most important factor for the patient is the final positive or negative determination.

If you receive an indeterminate result, you should repeat the test in 30 to 60 days. It is vital to follow up even if you aren't experiencing HIV symptoms like rapid weight loss, persistent fever, or skin rashes.

Rapid HIV tests

Rapid tests screen for HIV antibodies using a small saliva sample or a drop of blood. These tests provide results in 15 to 30 minutes and are highly reliable for screening purposes. The possible outcomes are:

• Positive: This suggests an infection is present. Because these are screening tests, a follow-up ELISA blood test is required to confirm the result.

• Negative: This indicates no antibodies were detected, meaning the person is likely not infected (provided they are outside the window period).

Rapid tests are frequently used in community outreach programs, mobile testing clinics, and in emergency settings, such as for pregnant women in labor who did not receive prior prenatal care.

What to do while waiting for results

If you believe you were recently exposed to HIV, do not wait for a standard test result. Go to an emergency room or urgent care clinic immediately to request Post-Exposure Prophylaxis (PEP), a medication regimen that can prevent the virus from taking hold.

PEP must be started within 72 hours of exposure to be effective, though starting within the first few hours offers the highest level of protection.

Why false negatives occur

A false negative usually occurs when a person tests too soon after a high-risk event, such as unprotected sex or sharing needles. During this early stage, the body has not yet produced enough antibodies or antigens for the test to see the virus.

In some cases, it can take the body up to three months to produce a detectable immune response. To be absolutely certain of a negative status, many health experts recommend a final confirmatory test 90 to 120 days after the potential exposure.

Viral load testing

The viral load test measures the number of copies of HIV in the blood. Its primary purpose is to monitor how the virus is progressing and to ensure that HIV medications are working effectively.

Because this test requires specialized molecular equipment and is expensive, it is not used as a primary screening tool for the general public. Instead, it is ordered for those already diagnosed with HIV, usually starting 2 to 8 weeks after diagnosis and every 3 months thereafter.

Common viral load ranges include:

• 100,000 to 1,000,000 copies: This is considered a high viral load, indicating a higher risk of transmission and disease progression.

• Under 10,000 copies: This suggests the virus is stable, with a lower risk of developing AIDS.

• Under 50 copies (undetectable): This means the virus is present in such small amounts that it cannot be measured by the test.

An undetectable result does not mean the person is cured; it means the treatment is working perfectly. When someone is undetectable, the risk of transmitting the virus through sex is effectively zero (U=U), though condom use is still recommended to prevent other STIs.

Physicians use these numbers to track treatment success. If the viral load rises, it may indicate the virus has become resistant to the current medication, and a change in the treatment plan may be necessary.