Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 23 peer-reviewed journal articles Updated
Infectious Disease · Acquired Immunodeficiency Syndrome (AIDS)

Navigating Your Lab Results

At a Glance

Reading HIV lab results starts with two markers: CD4 count, which reflects immune-system strength, and viral load, which measures HIV in the blood and treatment response. A CD4 below 200 signals advanced HIV/AIDS, while an undetectable viral load means treatment has suppressed HIV, not cured it.

Understanding your laboratory results is one of the most empowering steps you can take in managing your HIV care. These tests tell the story of how your immune system is faring and how well your treatment is working. Your doctors use a specific set of “baseline” labs to create a personalized treatment plan before you take your first dose of medication [1][2].

How HIV is Diagnosed

Modern HIV testing is highly accurate and designed to catch the virus much earlier than older tests. The standard is the 4th generation antigen/antibody test [3].

  • Antigens (p24): These are parts of the virus itself that appear in your blood very quickly after infection [4].
  • Antibodies: These are proteins your immune system makes to fight the virus. They take a bit longer to show up than antigens [5].

By looking for both, 4th generation tests can detect HIV (generally with an approximately 18-45 day window) [6]. If this test is positive, a follow-up test (differentiation assay) determines if you have HIV-1 or HIV-2. If results are unclear, or if you suspect very recent infection, an HIV RNA test (also called a nucleic acid test or NAT) is used to look for the virus’s genetic material directly, which is the earliest marker of infection [7][8].

Your Two Main Markers: CD4 and Viral Load

Once a diagnosis is confirmed, two specific tests become the foundation of your ongoing care: the CD4 count and the viral load.

1. CD4 Count: The Strength of Your Immune System

The CD4 count measures the number of CD4 T-cells in a microliter of blood. It is a snapshot of your immune system’s current health [9].

  • Healthy Range: Typically 500 to 1,500 cells/µL [10].
  • The AIDS Threshold: A CD4 count below 200 cells/µL, a CD4 percentage below 14%, or an AIDS-defining condition establishes a diagnosis of advanced HIV (AIDS) [9]. At this level, your risk for serious opportunistic infections increases significantly [11].
  • Recovery: As you start treatment, your CD4 count should gradually rise, showing that your immune system is repairing itself [12].

2. Viral Load (HIV RNA): The Speed of the Virus

The viral load measures how much of the virus is in your blood. This is the most important tool for monitoring how well your Antiretroviral Therapy (ART) is working [13].

  • Undetectable: This means the amount of virus is suppressed below the assay’s detection limit (usually fewer than 20 to 50 copies/mL, depending on the lab test) [14].
  • Suppression vs. Cure: Being undetectable does not mean you are cured; the virus is still “hiding” in latent reservoirs in your body, and stopping treatment will allow it to rebound [15].
  • U=U: Once you have been consistently suppressed for at least six months, you cannot transmit the virus to sexual partners [16].

Specialized Baseline Testing

Before starting ART, your doctor will run several specialized tests to ensure the chosen medication is safe and effective for you.

  • Resistance (Genotype) Testing: This test checks the “blueprint” of the virus in your body to see if it has any mutations that make it resistant to certain drugs [17]. It ensures you don’t start a medication that the virus has already learned to bypass [18].
  • Hepatitis B and C Screening: It is common for people to have HIV and Hepatitis at the same time. Because some HIV drugs also treat Hepatitis B, and some can affect the liver, knowing your Hepatitis status is vital for choosing the right regimen [19][20].
  • Organ Function: Tests for kidney function (creatinine) and liver function (ALT/AST) are done because your body must process HIV medications through these organs [21][22].

Your Baseline Evaluation Checklist

Before you begin your first ART regimen, your doctor will typically obtain the following baseline specimens. Note: ART generally should not be delayed while waiting for these results unless your clinician identifies a specific reason to do so [1].

  1. HIV Viral Load (Baseline level) [1]
  2. CD4 Count and Percentage [9]
  3. HIV Genotype (Resistance Test) (including an integrase genotype if prior PrEP/PEP was used) [17]
  4. Hepatitis B, C, and A Serology [20]
  5. Comprehensive Metabolic Panel (Kidney/Liver function, glucose/A1c) [21]
  6. Lipid Panel and Urinalysis
  7. Complete Blood Count (CBC) [22]
  8. Screening for STIs and Tuberculosis (TB) [23]
  9. HLA-B*5701 (if abacavir is being considered)
  10. Pregnancy Test (if applicable) [1]

Common questions in this guide

How is HIV diagnosed with blood tests?
A fourth-generation antigen/antibody test looks for both HIV p24 antigen and antibodies. If it is positive, a differentiation assay identifies HIV-1 or HIV-2; an HIV RNA test may be used when results are unclear or infection may be very recent.
What does a CD4 count below 200 mean?
A CD4 count measures immune-system cells that HIV can damage. A count below 200 cells per microliter, a CD4 percentage below 14%, or an AIDS-defining condition establishes advanced HIV or AIDS and increases the risk of opportunistic infections. The count can gradually improve with treatment.
What does an undetectable HIV viral load mean?
An undetectable viral load means the amount of HIV in the blood is below the test's detection limit, often about 20 to 50 copies per milliliter depending on the assay. It does not mean HIV is cured, because the virus can remain hidden and return if treatment is stopped. When suppression is maintained consistently for at least six months, HIV is not transmitted through sex, known as U=U.
Which lab tests are usually done before starting ART?
Baseline testing usually includes viral load, CD4 count and percentage, resistance genotype, hepatitis A, B, and C tests, kidney and liver function, a complete blood count, lipids, urinalysis, STI and tuberculosis screening, and a pregnancy test when applicable. HLA-B*5701 is checked if abacavir is being considered. ART generally should not be delayed while waiting for results unless a clinician identifies a specific reason.
Why is HIV resistance testing important?
A resistance genotype looks for changes in HIV that could make certain medications less effective. The results help clinicians choose drugs the virus is likely to respond to, and an integrase genotype may be added if you previously used PrEP or PEP.
What do kidney and liver tests show before HIV treatment?
Creatinine helps assess kidney function, while ALT and AST provide information about liver function. These results help your clinician choose HIV medicines that are safe for your body and identify medicines that may need to be avoided or monitored.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my current CD4 count, and does it mean I need to start medicine to prevent certain infections (prophylaxis)?
  2. 2.Is my viral load 'undetectable,' and what is the specific detection limit of the test you used?
  3. 3.Did my resistance (genotype) test show any mutations that limit which medications will work for me?
  4. 4.Based on my liver and kidney function tests, are there certain HIV medications I should avoid?
  5. 5.Since I am starting ART, when will we repeat these labs to see if the treatment is working?

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

References (23)
  1. 1

    Antiretroviral Drugs for Treatment and Prevention of HIV Infection in Adults: 2018 Recommendations of the International Antiviral Society-USA Panel.

    Saag MS, Benson CA, Gandhi RT, et al.

    JAMA 2018; (320(4)):379-396 doi:10.1001/jama.2018.8431.

    PMID: 30043070
  2. 2

    Antiretroviral Drugs for Treatment and Prevention of HIV Infection in Adults: 2016 Recommendations of the International Antiviral Society-USA Panel.

    Günthard HF, Saag MS, Benson CA, et al.

    JAMA 2016; (316(2)):191-210 doi:10.1001/jama.2016.8900.

    PMID: 27404187
  3. 3

    Human immunodeficiency virus: Diagnostic approach.

    Guarner J

    Seminars in diagnostic pathology 2017; (34(4)):318-324 doi:10.1053/j.semdp.2017.04.008.

    PMID: 28502523
  4. 4

    Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution.

    Alexander TS

    Clinical and vaccine immunology : CVI 2016; (23(4)):249-53 doi:10.1128/CVI.00053-16.

    PMID: 26936099
  5. 5

    Time Until Emergence of HIV Test Reactivity Following Infection With HIV-1: Implications for Interpreting Test Results and Retesting After Exposure.

    Delaney KP, Hanson DL, Masciotra S, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2017; (64(1)):53-59 doi:10.1093/cid/ciw666.

    PMID: 27737954
  6. 6

    Screening Yield of HIV Antigen/Antibody Combination and Pooled HIV RNA Testing for Acute HIV Infection in a High-Prevalence Population.

    Peters PJ, Westheimer E, Cohen S, et al.

    JAMA 2016; (315(7)):682-90 doi:10.1001/jama.2016.0286.

    PMID: 26881371
  7. 7

    Evaluation of Xpert HIV-1 Qual assay for resolution of HIV-1 infection in samples with negative or indeterminate Geenius HIV-1/2 results.

    Michaeli M, Wax M, Gozlan Y, et al.

    Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology 2016; (76()):1-3.

    PMID: 26761545
  8. 8

    Prospective Study of Acute HIV-1 Infection in Adults in East Africa and Thailand.

    Robb ML, Eller LA, Kibuuka H, et al.

    The New England journal of medicine 2016; (374(22)):2120-30 doi:10.1056/NEJMoa1508952.

    PMID: 27192360
  9. 9

    Utility of CD4 count measurement in the era of universal antiretroviral therapy: an analysis of routine laboratory data in Botswana.

    Leeme TB, Mine M, Lechiile K, et al.

    HIV medicine 2021; (22(1)):1-10 doi:10.1111/hiv.12951.

    PMID: 32876378
  10. 10

    Trends in Time From HIV Diagnosis to First Viral Suppression Following Revised US HIV Treatment Guidelines, 2012-2017.

    Crepaz N, Song R, Lyss S, Hall HI

    Journal of acquired immune deficiency syndromes (1999) 2020; (85(1)):46-50 doi:10.1097/QAI.0000000000002398.

    PMID: 32379083
  11. 11

    Suboptimal immune recovery during antiretroviral therapy with sustained HIV suppression in sub-Saharan Africa.

    Kroeze S, Ondoa P, Kityo CM, et al.

    AIDS (London, England) 2018; (32(8)):1043-1051 doi:10.1097/QAD.0000000000001801.

    PMID: 29547445
  12. 12

    Five-Year Immune Recovery After ART Initiation Among PLWH Aged ≥15 Years with Baseline Immunosuppression - China, 2013-2024.

    Geng Y, Jia H, Guan Y, et al.

    China CDC weekly 2026; (8(25)):772-779 doi:10.46234/ccdcw2026.125.

    PMID: 42433220
  13. 13

    Progress with Scale-Up of HIV Viral Load Monitoring - Seven Sub-Saharan African Countries, January 2015-June 2016.

    Lecher S, Williams J, Fonjungo PN, et al.

    MMWR. Morbidity and mortality weekly report 2016; (65(47)):1332-1335 doi:10.15585/mmwr.mm6547a2.

    PMID: 27906910
  14. 14

    Undetectable proviral deoxyribonucleic acid in an adolescent perinatally infected with human immunodeficiency virus-1C and on long-term antiretroviral therapy resulted in viral rebound following antiretroviral therapy termination: A case report with implications for clinical care.

    Koofhethile CK, Moyo S, Kotokwe KP, et al.

    Medicine 2019; (98(47)):e18014 doi:10.1097/MD.0000000000018014.

    PMID: 31764816
  15. 15

    Advances in Developing CAR T-Cell Therapy for HIV Cure.

    Qi J, Ding C, Jiang X, Gao Y

    Frontiers in immunology 2020; (11()):361 doi:10.3389/fimmu.2020.00361.

    PMID: 32210965
  16. 16

    Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.

    Rodger AJ, Cambiano V, Bruun T, et al.

    Lancet (London, England) 2019; (393(10189)):2428-2438 doi:10.1016/S0140-6736(19)30418-0.

    PMID: 31056293
  17. 17

    Transmitted Drug Resistance Among Human Immunodeficiency Virus (HIV)-1 Diagnoses in the United States, 2014-2018.

    McClung RP, Oster AM, Ocfemia MCB, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2022; (74(6)):1055-1062 doi:10.1093/cid/ciab583.

    PMID: 34175948
  18. 18

    Should We Be Testing for Baseline Integrase Resistance in Patients Newly Diagnosed With Human Immunodeficiency Virus?

    Koullias Y, Sax PE, Fields NF, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2017; (65(8)):1274-1281 doi:10.1093/cid/cix542.

    PMID: 28605418
  19. 19

    Risk of End-Stage Liver Disease in HIV-Viral Hepatitis Coinfected Persons in North America From the Early to Modern Antiretroviral Therapy Eras.

    Klein MB, Althoff KN, Jing Y, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2016; (63(9)):1160-1167 doi:10.1093/cid/ciw531.

    PMID: 27506682
  20. 20

    The 2018 Clinical Guidelines for the Diagnosis and Treatment of HIV/AIDS in HIV-Infected Koreans.

    Infection & chemotherapy 2019; (51(1)):77-88 doi:10.3947/ic.2019.51.1.77.

    PMID: 30941943
  21. 21

    Imbalance of antioxidant enzymes activities and trace elements levels in Ghanaian HIV-infected patients.

    Quaye O, Kuleape JA, Bonney EY, et al.

    PloS one 2019; (14(7)):e0220181 doi:10.1371/journal.pone.0220181.

    PMID: 31339937
  22. 22

    The first report of kidney transplantation in a human immunodeficiency virus-positive recipient in Thailand and literature review: Encouragement for developing countries in Southeast Asia.

    Udomkarnjananun S, Naiyarakseree N, Townamchai N, et al.

    SAGE open medical case reports 2021; (9()):2050313X211024471 doi:10.1177/2050313X211024471.

    PMID: 34211716
  23. 23

    Epidemiological characteristics of HIV infected Korean: Korea HIV/AIDS Cohort Study.

    Choi Y, Choi BY, Kim SM, et al.

    Epidemiology and health 2019; (41()):e2019037 doi:10.4178/epih.e2019037.

    PMID: 31623426

This page explains common HIV and AIDS laboratory tests for informational purposes only and does not constitute medical advice. Ask your HIV clinician to interpret your results and plan your care.

Get notified when new evidence is published on AIDS.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.