Blood tests on HIV PrEP
For anyone taking PrEP to prevent HIV, whether daily pills such as Truvada or Descovy, or shots such as cabotegravir or lenacapavir.
11 tests explainedAI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-19
PrEP comes with a regular schedule of tests. Each visit includes an HIV test, because PrEP is only for people who don't have HIV. Daily pills also come with kidney checks, and Descovy with yearly cholesterol checks. Hepatitis B testing at the start and regular testing for common sexually transmitted infections (STIs) are part of routine PrEP care.
The tests that matter most
Most important first. Each one links to its full page, where the note for this group sits near the top.
HIV-1/2 Antigen/Antibody (4th Generation)
An HIV test comes right before starting PrEP and at follow-up visits. The CDC suggests testing at least every 3 months on daily pills and every 2 months with cabotegravir shots. With lenacapavir shots, a test is done before each 6-month injection.
Sources: Centers for Disease Control and Prevention (2021), Centers for Disease Control and Prevention (2025) and U.S. National Library of Medicine (2026)
HIV-1 RNA (Quantitative Viral Load)
An HIV RNA test looks for the virus itself. PrEP medicines can delay antibody tests turning positive, so the CDC lists an RNA test alongside the antigen/antibody test at PrEP visits.
Sources: Centers for Disease Control and Prevention (2021) and Centers for Disease Control and Prevention (2025)
Creatinine
Truvada (F/TDF) has caused small drops in kidney function that mostly reversed after stopping. The CDC suggests a kidney check before starting pills, then every 6 months for people 50 or older or with lower kidney function at the start, and every 12 months for everyone else. The CDC schedule for cabotegravir shots doesn't include kidney checks.
Sources: Centers for Disease Control and Prevention (2021) and U.S. National Library of Medicine (2026)
- Men, 15+
- 0.74–1.35 mg/dL
- Women, 16+
- 0.59–1.04 mg/dL
eGFR (Creatinine-based)
The CDC judges kidney function on PrEP pills by estimated creatinine clearance, worked out with the Cockcroft-Gault formula from creatinine, age, sex and an ideal weight based on height. The eGFR on most lab reports comes from a different equation and is scaled to a standard body size, so the two numbers can differ.
Sources: Centers for Disease Control and Prevention (2021) and KDIGO (2024)
- Usual adult range
- 60 and above mL/min/1.73 m²
Hepatitis B Surface Antigen (HBsAg)
The pill forms of PrEP also treat hepatitis B. In someone with hepatitis B, stopping them can cause a flare of liver inflammation, so the CDC suggests hepatitis B testing before starting.
Sources: Centers for Disease Control and Prevention (2021), Centers for Disease Control and Prevention (2025) and U.S. National Library of Medicine (2026)
Hepatitis B Surface Antibody (Anti-HBs)
Anti-HBs shows protection against hepatitis B. The CDC guideline says people on PrEP who aren't immune and don't have hepatitis B should be offered the vaccine.
- Usual adult range
- 10 and above mIU/mL
Hepatitis C Antibody
The CDC suggests hepatitis C testing before starting and every 12 months for gay, bisexual and other men who have sex with men, transgender women who have sex with men, and people who inject drugs.
Triglycerides
In a large trial, men taking Descovy (F/TAF) had more triglyceride rises and weight gain than men taking Truvada. The CDC suggests checking triglycerides, cholesterol and weight every 12 months on Descovy.
- Usual adult range
- up to 149 mg/dL
RPR (Rapid Plasma Reagin)
Syphilis is checked with a blood test as part of routine PrEP care. For people on pills, the CDC schedule is every 3 months for men who have sex with men and transgender women who have sex with men, and every 6 months for other sexually active people. Cabotegravir and lenacapavir shots have their own schedules.
Sources: Centers for Disease Control and Prevention (2021) and Centers for Disease Control and Prevention (2025)
Neisseria gonorrhoeae NAAT
Gonorrhea testing follows the same schedule as syphilis in the CDC guideline. Depending on the kind of sex someone has, swabs from the throat or rectum may be used as well as urine.
Chlamydia trachomatis NAAT
For people on pills, the CDC suggests chlamydia testing every 3 months for men who have sex with men and transgender women who have sex with men, and every 12 months for heterosexually active women and men, even without symptoms.
Ranges shown are the usual adult ranges labs print. The range on your own report is the one your result is judged against.
Getting results you can compare
- On daily pills, the CDC links each prescription to an HIV test, with no more than a 90-day supply until the next test.
- If kidney results drift down over time, the CDC guideline suggests clinicians ask about high doses of anti-inflammatory pain relievers (NSAIDs) or protein powders as possible causes.
- With lenacapavir, the CDC suggests STI screening at each 6-month visit and notes it may need to happen more often than the shots, depending on risk.
Good to know
- PrEP medicines aren't enough to treat HIV, and taking them with an undetected infection can lead to drug resistance. That is why an HIV test comes before every PrEP prescription or shot.
Sources: Centers for Disease Control and Prevention (2021) and U.S. National Library of Medicine (2026)
- The CDC's 2021 guideline covers PrEP pills and cabotegravir shots, and a 2025 CDC update added lenacapavir. Schedules can change as new options arrive, so the clinic's plan may differ a little from what's here.
Sources: Centers for Disease Control and Prevention (2021) and Centers for Disease Control and Prevention (2025)
Questions you could ask
- Which tests will we do at each PrEP visit, and how often?
- Which STI tests make sense for me, and which sample types?
- How is my kidney function looking compared with when I started?
- Am I protected against hepatitis B?
Sources
- Preexposure Prophylaxis for the Prevention of HIV Infection in the United States: 2021 Update. A Clinical Practice Guideline, Centers for Disease Control and Prevention (2021)
- Clinical Recommendation for the Use of Injectable Lenacapavir as HIV Preexposure Prophylaxis: United States, 2025, Centers for Disease Control and Prevention (2025)
- Descovy (emtricitabine and tenofovir alafenamide) tablets: prescribing information, U.S. National Library of Medicine (2026)
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, KDIGO (2024)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-19. How we build and check these pages.
Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.