Premarital Blood Tests and Couples STI Testing: What to Test

Many couples tell me, "We'd like to get tested before the wedding, but I'm afraid my partner will think I don't trust them." I understand that feeling. But look at it another way: getting tested together says "we're going to look after each other for the long term", not "I'm checking up on you". And testing before planning a baby helps prevent many avoidable problems. This article applies to couples of every gender, whether you're registering your marriage under the Marriage Equality Act or have just started a serious relationship.

Part 1: STI testing (every couple should test)

1. HIV. A fourth-generation Ag/Ab blood test. If one partner has HIV, treatment to an undetectable viral load means it isn't passed on through sex. Read U=U: undetectable equals untransmittable.
2. Syphilis. An RPR/VDRL blood test together with a specific test such as TPHA. This is very important before pregnancy, because syphilis can pass to the baby. See syphilis.
3. Hepatitis B. HBsAg and immunity (anti-HBs). If you aren't immune, get vaccinated; if your partner carries the virus, vaccination is even more important.
4. Hepatitis C. Anti-HCV. It can now be cured with oral medication.
5. Gonorrhoea and chlamydia. PCR testing of urine or swabs, plus throat or rectal swabs according to the type of sex you have. See the PCR STI test.
6. Trichomoniasis, especially if there is abnormal discharge or risk.

What about HPV and herpes?

• HPV. There's no blood test for HPV screening. Women have cervical cancer screening according to their age, and the best prevention is the HPV vaccine for both partners.
• Herpes. International guidelines don't recommend herpes blood tests for people without symptoms, because many people already have antibodies to HSV-1 and a blood result doesn't tell you when or from whom it was caught. If either of you has had herpes sores, talking openly and planning prevention is more useful. Read more in herpes.

Part 2: Tests for planning a family

1. ABO and Rh blood group. If the woman is Rh negative, the pregnancy needs monitoring.
2. Complete blood count (CBC) to check for anaemia, with MCV/MCH values that help screen for thalassaemia.
3. Thalassaemia carrier status. Haemoglobin typing (Hb typing) plus further tests where indicated. Thalassaemia carriers are very common in Thailand and across Southeast Asia. If both partners carry the same type, the child may have a severe form of the disease, which can be planned for if you know in advance.
4. Rubella immunity (Rubella IgG). If you aren't immune, get vaccinated and wait before conceiving as your doctor advises.
5. Blood sugar and blood pressure, especially for people who are overweight or have a family history.
6. Others as appropriate, such as thyroid function, a pelvic exam and cervical screening, or semen analysis if there are fertility problems. See semen analysis.

For couples where one partner has HIV and they want children, this can now be planned safely. Read HIV and having children.

Long-term couples, open relationships and LGBTQ+ couples

• Long-term monogamous couples. If you've both had full tests with negative results, you might retest only when there's a reason for concern, or as part of annual check-ups.
• Open relationships. Agree on prevention rules together and test every 3–6 months. Consider PrEP for anyone with ongoing risk.
• Male couples or couples who have anal sex. Add rectal and throat swabs, because a urine test alone can miss a lot.

Tips before you go for testing

• Choose a time when neither of you has had a new risk in the 2–6 weeks before testing, or tell your doctor if you have, because some infections may still be in the window period when tests can't detect them. Read HIV incubation and window periods.
• You don't need to fast, unless you're having a fasting glucose or lipid test.
• Agree beforehand whether you'll look at results together or separately. Respecting each person's privacy matters as much as the results.

When to see a doctor, and how the clinic can help

If you're planning to marry, have children or start a new relationship, test at least 3–6 months in advance so there's time to catch up on vaccines and treat anything that's found. At Dr. Kris Clinic in Surat Thani, I put together a test list to suit each couple without over-testing, offer joint counselling and can plan vaccinations straight away, as well as helping with conversations that are hard for couples to start through couples counselling. English-speaking consultations are available in person and online.