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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Infectious Disease · Human Immunodeficiency Virus Infection

Your Essential Baseline Labs and Testing

At a Glance

Before starting HIV treatment, baseline testing usually includes CD4 count, viral load, drug-resistance testing, hepatitis screening, kidney and liver checks, blood counts, and other safety tests. Follow-up labs show whether ART is working and well tolerated.

Before you start Antiretroviral Therapy (ART), your medical team needs a clear snapshot of your health. These baseline tests ensure the medications chosen for you are safe, effective, and tailored to your specific needs [1][2].

The Big Two: CD4 and Viral Load

Two tests are the cornerstones of HIV monitoring. They tell your doctor how the virus is behaving and how your immune system is responding.

  • CD4 T-lymphocyte Count: This measures the number of CD4 cells (helper T cells) in your blood. It acts as an indicator for your immune system, pointing out your current level of protection against infections [3]. While a normal count is typically 500–1,500, treatment is recommended regardless of how high or low this number is [4].
  • HIV RNA (Viral Load): This measures the amount of HIV in your blood. It is the most direct way to see how active the virus is [5]. The goal of treatment is to make this number so low that it becomes undetectable (usually fewer than 20–50 copies per milliliter, depending on the lab’s equipment) [6].

Tailoring Your Treatment: Resistance and Genetic Testing

Not every HIV medication works for every person. These tests help your doctor prescribe with precision.

  • Genotypic Resistance Testing: This test analyzes the specific strain of HIV in your body to see if it has mutations that make it resistant to certain drugs [7]. It is standard to order this at your first visit [8]. In most cases, your doctor will not delay starting treatment while waiting for these results, and can adjust the regimen if necessary [9].
  • HLA-B*57:01 Testing: This is a genetic test for you, not the virus. It checks for a specific genetic marker that makes you highly likely to have a severe allergic reaction to a drug called abacavir (found in medications like Triumeq) [10]. If you test positive, you must never take abacavir [11].

Screening for Other Infections and Organ Health

Because HIV is an immune system condition, it is vital to know if your body is dealing with other infections at the same time.

  • Hepatitis B (HBV) and C (HCV): These viruses affect the liver. It is critical to have a complete HBV panel (HBsAg, total anti-HBc, and anti-HBs) because some HIV medications also treat HBV, and an incomplete panel could miss an occult infection leading to an HBV flare [12]. For HCV, a positive antibody test requires a reflex HCV RNA test to confirm current infection [13].
  • Tuberculosis (TB) and Syphilis: HIV increases the risk of active TB, so screening is recommended for everyone at diagnosis [14]. Site-specific screening for syphilis, gonorrhea, and chlamydia is also standard because these can impact your overall health [1].

Your Baseline Completeness Checklist

When you receive your first large batch of lab results, look for these key items:

  1. HIV-1 RNA (Viral Load) [1]
  2. CD4 Count and Percentage [3]
  3. HIV Genotype (Resistance Report) [8]
  4. Complete Hepatitis B Panel (HBsAg, total anti-HBc, anti-HBs) [12]
  5. Hepatitis C Antibody (with reflex HCV RNA if positive) [13]
  6. HLA-B*57:01 (especially if abacavir is being considered) [10]
  7. Comprehensive Metabolic Panel (checking kidney eGFR and liver function) and Urinalysis [15]
  8. Complete Blood Count (CBC) (checking for anemia or low white blood cells) [16]
  9. Lipid panel and Glucose/A1c
  10. Syphilis, gonorrhea, chlamydia, and TB screening [17][14]
  11. Pregnancy testing (when clinically relevant)

Ongoing Monitoring

Once you start ART, your doctor will check your labs frequently at first—often within 2 to 8 weeks—to ensure your viral load is dropping and your body is tolerating the medicine [2]. Once your viral load is consistently undetectable and your health is stable, these check-ups typically move to every 3 to 6 months [18]. Over time, if you remain stable for a year or more, your doctor may decide that CD4 monitoring is no longer needed at every visit, focusing instead on your viral load [3].

Common questions in this guide

Which tests are usually done before starting HIV treatment?
Baseline testing commonly includes an HIV RNA viral load, CD4 count and percentage, a genotype resistance report, hepatitis B and C tests, kidney and liver checks, a blood count, and other safety screening. Depending on your situation, testing may also include HLA-B*57:01, pregnancy, glucose or A1c, lipid, tuberculosis, syphilis, gonorrhea, and chlamydia tests.
How are a CD4 count and viral load different?
A CD4 count measures helper T cells and gives an indication of how well your immune system is protected. A viral load measures the amount of HIV in your blood, and the goal of antiretroviral therapy is to reduce it to an undetectable level.
Why is HIV genotype testing done before choosing medicines?
A genotype test looks for changes in HIV that can make particular medicines less effective. Treatment often starts before the result is available, and your clinician can adjust the regimen if the report shows drug resistance.
What does a positive HLA-B*57:01 result mean?
A positive result means you have a genetic marker linked to a high risk of a severe allergic reaction to abacavir. People with a positive HLA-B*57:01 result must not take abacavir, including abacavir-containing medicines such as Triumeq.
Why are hepatitis and sexually transmitted infection tests part of HIV care?
Hepatitis B and C can affect the liver, and some HIV medicines also treat hepatitis B, so these results help guide medication choices and prevent complications. Screening for tuberculosis, syphilis, gonorrhea, and chlamydia helps identify infections that may need treatment alongside HIV.
When are HIV labs repeated after starting ART?
Labs are often repeated within 2 to 8 weeks after starting antiretroviral therapy to check that the viral load is falling and the medicine is tolerated. Once your viral load and health are stable, visits commonly occur every 3 to 6 months, and CD4 testing may become less frequent after a sustained period of stability.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Can you walk me through my CD4 count and viral load results and what they say about my current immune health?
  2. 2.Did my genotype test show any resistance to the medications we are considering?
  3. 3.Since I'm starting on a new regimen, was an HLA-B*57:01 test performed, and what was the result?
  4. 4.What were my Hepatitis B and C results, and how do they affect which HIV medications are safest for me?
  5. 5.Based on these initial labs, how often will I need to come back for blood work during my first year of treatment?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

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This page is for informational purposes only and does not constitute medical advice. Your HIV clinician should interpret your baseline results and decide which tests and treatments are appropriate for you.

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