References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Before starting HIV treatment or switching to a new regimen, your clinic will run a series of blood tests. These baseline measurements help your doctor choose the right drugs for you, check for coexisting conditions, and monitor your response to treatment over time.
Understanding what’s being tested and why can help you feel more informed and in control of your care.
Standard Pre-Treatment Blood Tests
| Test | What It Measures | Why It Matters |
|---|---|---|
| HIV viral load | Amount of HIV in the blood | Baseline for monitoring treatment response |
| CD4 count | Number of CD4 T-cells | Measures immune system health |
| HIV resistance test (genotype) | Genetic mutations in HIV | Identifies drugs that may not work |
| Full blood count (FBC) | Red cells, white cells, platelets | Baseline for monitoring drug side effects |
| Liver function (LFTs) | Liver enzymes, bilirubin | Some HIV drugs affect the liver |
| Kidney function (eGFR, creatinine) | Kidney filtration rate | Some drugs require dose adjustment if kidneys are impaired |
| Lipid profile | Cholesterol, triglycerides | Some drugs affect lipids |
| Blood glucose | Sugar levels | Some drugs can affect glucose metabolism |
| HLA-B*5701 | Genetic marker | Identifies people at risk of abacavir hypersensitivity |
| Hepatitis B and C screening | Co-infection status | Affects drug choice and treatment strategy |
| Vitamin D | Blood levels | Deficiency is common in HIV; affects bone health |
Additional Tests
Depending on your circumstances, your doctor may also request:
- Tuberculosis screening (especially if you’re from a high-TB-prevalence area)
- Syphilis and other STI tests
- Hepatitis A immunity (to guide vaccination)
- Cervical screening (women)
- Tropism test (if maraviroc is being considered)
Why These Tests Matter
The baseline tests serve two purposes: they help choose the safest and most effective treatment for you, and they give your doctor a starting point to compare future tests against. If your CD4 count rises from 250 to 600 over 12 months, that’s clear evidence the treatment is working. Without the baseline, you wouldn’t know.
Read more: What is HIV? | Starting HIV treatment | CD4 counts explained
Frequently Asked Questions
How long before starting treatment will I have these tests?
Usually within 1-2 weeks of diagnosis or when planning a drug switch. Results come back within a few days to a week, and your doctor uses them to finalise your treatment choice.
Do I need to fast for these tests?
Most HIV-related blood tests don’t require fasting. However, if your lipid profile and glucose are being tested, you may be asked to fast for 8-12 hours beforehand. Your clinic will tell you if fasting is needed.
Will I need these tests repeated?
Yes, most are repeated regularly. Viral load and CD4 count are checked every 3-6 months. Other tests (liver, kidney, lipids) are checked annually or more often if there’s a concern.
Related reading
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
- How Accurate Are Rapid HIV Tests?
- Injectable HIV Treatment: Everything You Need to Know
- Anonymous STI Testing: What It Means
- Are STI Blood Tests Accurate?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
