Private STI Blood Test UK (2026): HIV, Syphilis, Hepatitis — Costs, NHS vs Private, Window Periods
Short version: NHS sexual health clinics offer comprehensive free STI testing with same-day or rapid results across the UK, plus free postal home test kits in most regions. The NHS pathway is the right first choice for most people: free, fast, confidential, and treatment is included if anything is positive. Private STI blood testing (£49–£299) mainly competes on speed, the in-person clinic experience, or specific combinations of tests not always available NHS. Blood tests cover HIV, syphilis, hepatitis B and C — chlamydia and gonorrhoea are urine/swab tests, not blood. Modern HIV tests are reliable from 4 weeks post-exposure; syphilis from 6 weeks; hepatitis B/C from 4–12 weeks. Don't test too early.
Sexually transmitted infection testing is one of the few areas where the NHS service is genuinely excellent: free, fast, comprehensive, confidential, and treatment is included. Private STI testing exists in parallel and serves some legitimate use cases, but for the majority of people the NHS sexual health route is the right starting point. This guide covers what each blood test does, when to test, the realistic window periods, and where private testing actually adds value.
What blood STI testing covers
Blood-based STI tests detect four major infections:
- HIV — detected by combined antibody + p24 antigen (4th generation) or antibody-only (3rd generation) tests.
- Syphilis — detected by treponemal antibody tests (TPHA, TPPA, EIA), with non-treponemal tests (RPR, VDRL) used to assess disease activity.
- Hepatitis B — detected by hepatitis B surface antigen (HBsAg) for active infection, with anti-HBs and anti-HBc for vaccination status and past exposure.
- Hepatitis C — detected by hepatitis C antibody, with HCV RNA (viral load) confirming active infection if antibody is positive.
What blood testing does not cover:
- Chlamydia — diagnosed by urine or swab.
- Gonorrhoea — urine or swab.
- Trichomonas — urine or swab.
- Herpes (HSV-1, HSV-2) — usually diagnosed by swab of active lesions; antibody blood tests exist but their interpretation is controversial (positive antibodies indicate exposure not active disease).
- HPV — diagnosed by cervical/anal swab; no routine blood test in standard sexual health screening.
- Mycoplasma genitalium — urine or swab PCR.
A "comprehensive STI test" usually combines blood with urine and swab samples to cover the full range. A "blood STI panel" by itself covers the four above and is meaningfully narrower.
Window periods — when to test
Window period = the time between potential exposure and when the test reliably detects the infection. Testing too early can produce a falsely reassuring negative result. UK window periods for routine blood STI tests in 2026:
| Infection | Earliest reliable test | Definitive test |
|---|---|---|
| HIV (4th-gen Ag/Ab) | 2–4 weeks | 3 months |
| HIV (3rd-gen Ab) | 4–6 weeks | 3 months |
| HIV (RNA viral load) | 10 days | 3 months |
| Syphilis (treponemal antibody) | 3–6 weeks | 3 months |
| Hepatitis B (HBsAg) | 4 weeks | 3 months |
| Hepatitis C (antibody) | 4–12 weeks | 3 months |
| Hepatitis C (RNA) | 1–2 weeks | 3 months |
Practical guidance:
- For a one-off potential exposure with no symptoms: test at 4–6 weeks, repeat at 3 months.
- If symptoms develop (rash, fever, lymphadenopathy, urethral discharge) at any time: test immediately regardless of window period — and seek clinical assessment.
- If the exposure was within 72 hours: HIV PEP is available free from sexual health clinics and A&E. 28-day course of antiretrovirals that significantly reduces seroconversion risk.
- If you've had repeated exposures or are on PrEP: NHS sexual health screening at the recommended cadence (3-monthly for many PrEP users).
When private STI testing makes sense
Five scenarios where paying for private STI testing is reasonable:
- You want results faster than your local NHS sexual health clinic can offer. Waiting times vary by region; some clinics offer same-day, others 1–3 weeks for routine appointments. Same-day private testing in central London is reliably available.
- You want a specific test combination the NHS doesn't routinely offer. For example, HSV antibody panels (debated utility), or extended hepatitis profiles beyond surface antigen.
- You're abroad or moving between regions and can't easily access an NHS sexual health clinic in your area.
- You want a one-off baseline test in a new relationship and prefer the privacy of home testing.
- You want home fingerprick/dried-blood-spot testing and your region doesn't offer NHS home test kits. (Increasingly rare — NHS home testing has expanded substantially in 2023–2026.)
When private testing is unnecessary:
- NHS sexual health is available in your area with reasonable timing — it's genuinely better value.
- You need comprehensive testing including chlamydia and gonorrhoea — NHS clinics combine all routes in one visit.
- You're symptomatic — NHS sexual health offers fast access for symptomatic presentations and includes treatment.
- You may need partner notification — NHS sexual health has structured contact-tracing support.
UK private STI test costs in 2026
| Test | Markers | Typical price |
|---|---|---|
| Single HIV blood test | HIV 4th-gen | £29–£49 |
| Single syphilis blood test | Treponemal antibody | £29–£59 |
| Hepatitis B blood test | HBsAg | £39–£69 |
| Hepatitis C blood test | Antibody | £39–£69 |
| 4-in-1 blood STI panel | HIV + syphilis + HBV + HCV | £89–£149 |
| Comprehensive STI panel (blood + urine + swab) | Above + chlamydia + gonorrhoea + trichomonas | £149–£299 |
| Premium clinic STI screen with consultation | Comprehensive + clinician input | £200–£500 |
| NHS sexual health (clinic or home kit) | Comprehensive blood + urine + swab | £0 |
UK private STI testing providers
Medichecks
Single STI tests at £29–£69 and combined STI Profile at ~£99. Fingerprick or venous, UKAS-accredited lab. Best for blood-only panels. Medichecks catalogue.
Better2Know
Specialist private STI testing provider with one of the broadest STI menus in the UK. Comprehensive STI panels including blood and swab samples. £49–£399 depending on breadth. Clinic network across major cities.
Forth
Individual STI blood tests; Forth's main strength is hormone testing rather than STI panels. Reasonable single-test option. Forth's range.
Thriva
Limited STI catalogue compared to Medichecks and Better2Know. Best when you specifically want a single marker integrated with their broader health tracking. Thriva's tests.
Randox Health
Clinic-based testing at London, Liverpool and Manchester locations including STI panels. Same-day results for most blood markers. £150–£500 packages.
The NHS sexual health pathway — why it's usually the right choice
NHS sexual health services across the UK offer:
- Comprehensive testing — HIV, syphilis, hepatitis, chlamydia, gonorrhoea, trichomonas, herpes (swab where indicated), mycoplasma genitalium (region-dependent), HPV (cervical/anal swab where appropriate).
- Rapid HIV testing with results in 60 minutes at many clinics.
- Free home testing kits via SH:24 (England), Sexual Health London, Fettle, Free Test Me, and regional equivalents.
- Confidential service separate from your GP record unless you opt in.
- Anonymous booking in many areas — you can use a pseudonym.
- Free treatment for everything testable.
- Partner notification support — anonymous contact tracing if you wish.
- PEP and PrEP access — post-exposure and pre-exposure HIV prophylaxis, free.
- Vaccination — hepatitis A, hepatitis B, HPV, mpox where indicated.
The main reasons private testing competes:
- Speed of appointment in some regions where NHS waiting times are longer.
- The perception of greater privacy (though NHS is genuinely confidential).
- Specific testing combinations not always run by NHS (e.g. HSV serology — debated utility).
- One-stop clinic experience with same-day results in central London.
When to seek immediate testing rather than wait
Don't wait for window periods if you have:
- Unusual urethral or vaginal discharge.
- Pain on urination not explained by UTI.
- Genital ulcers or rashes.
- Fever, lymph node swelling and rash 2–4 weeks after potential exposure (could be seroconversion illness).
- Pelvic pain or testicular pain.
- Eye inflammation in the context of recent exposure.
Go to NHS sexual health or your GP for assessment — empirical treatment may be appropriate pending test results.
After a positive result
Practical steps if any STI test returns positive:
- Confirm the result. Most providers offer confirmatory testing for positive results, especially for HIV (very rare false positives but they exist) and hepatitis C (antibody positive doesn't mean active infection — RNA needed). Don't share or worry about a single unconfirmed result.
- Engage with NHS sexual health. All STI treatment is free. NHS clinics will accept private test results as the basis for assessment. Treatment for HIV is now highly effective — modern antiretroviral therapy means undetectable viral loads within months, normal life expectancy, and effectively zero transmission risk to sexual partners. Syphilis treatment is a course of penicillin injections. Hepatitis B is managed with antiviral suppression (lifelong in most cases). Hepatitis C is now curable in 8–12 weeks with direct-acting antivirals (DAAs) — >95% cure rates.
- Partner notification. NHS sexual health services offer anonymous contact tracing — partners can be informed they may have been exposed without your identity being disclosed.
- Follow-up testing. Some infections require ongoing monitoring after treatment (syphilis non-treponemal titres, hepatitis C cure confirmation, HIV viral load).
- Mental health and support. A positive result can be emotionally difficult — sexual health services and charities (Terrence Higgins Trust, British Liver Trust) offer free support.
How often to test
General guidance:
- Annual screening for sexually active adults under 25, sex workers, and people with multiple recent partners.
- 3-monthly for people taking HIV PrEP, men who have sex with men with multiple partners, and after diagnosis of any STI.
- At change of partner — common-sense baseline at the start of new sexual relationships, ideally for both partners.
- After potential exposure — at appropriate window period.
- Annually in pregnancy — NHS antenatal screening includes HIV, syphilis, hepatitis B, plus chlamydia and rubella; private testing rarely needed.
Related guides
- Private blood tests UK pillar — broader context.
- Liver health blood test UK — hepatitis screening overlap.
- Private cardiovascular risk test UK — long-untreated HIV elevates cardiovascular risk; relevant once status is known.
- Private blood test cost UK — pricing across providers.
- Private vs NHS — pathway comparison.
- Private blood test London — same-day options in the capital.
- Can I pay for an NHS blood test? — NHS pricing question.