What blood tests should I get before trying to get pregnant?
Before trying to get pregnant, ask for a TSH (thyroid) test, ferritin plus a blood count (iron stores), and an A1c (blood sugar) if you have risk factors. Ask whether vitamin D and B12 tests make sense, and get STI tests for both partners. Optional carrier screening shows shared inherited risks. Book it about three months ahead.
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The tests to ask for by name
A preconception visit is an ordinary appointment with your family doctor, OB/GYN, nurse practitioner or midwife. Say, “We're planning to try for a baby in the next few months. What should we check?” Then name these tests. Most are simple blood draws, and many problems they find are easy to treat.
| Test | What it shows | What to ask |
|---|---|---|
| TSH (thyroid) | Whether your thyroid runs slow; thyroid hormone helps build the baby's brain | “What level do you want before I conceive?” |
| Ferritin and blood count | Your iron stores, before anemia appears | “Can you include ferritin, not just hemoglobin?” |
| A1c | Average blood sugar over the past two to three months | “What's my A1c? If I have diabetes, what target do you want before I try?” |
| Vitamin D | Whether you run low; low levels are common | “Should I be tested, or just supplement?” |
| Vitamin B12 | Low levels in vegans, vegetarians and metformin users | “Can you check my B12?” |
| STI tests (both partners) | Infections that can pass to the baby | “Can we both be tested for syphilis, HIV, hepatitis B and C, chlamydia and gonorrhea?” |
| Carrier screening (optional) | Whether you both carry a gene change for the same inherited condition | “Is it offered and covered? Can I see a genetic counselor?” |
Thyroid and iron: the two the early brain leans on
Thyroid. TSH goes up when your thyroid runs slow. About 2.5% of pregnant women have a slightly high TSH (above 6), according to the American Thyroid Association. It's easy to miss, because tiredness and weight gain are easy to blame on life. Early in pregnancy your baby can't make its own thyroid hormone and depends entirely on yours, which is why knowing your level before pregnancy helps. More in getting your thyroid checked.
Iron. A standard blood count looks at hemoglobin, which only falls after your iron stores are used up. Ferritin measures the stores themselves, and the NIH says it can show iron running low early, before anemia appears. Stores drain fast in pregnancy: in US data, 18% of pregnant women were iron deficient, rising from 6.9% in the first trimester to 29.7% in the third. Heavy periods and a vegetarian diet make a low start more likely. See checking iron before pregnancy.
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Blood sugar: the check people skip most
An A1c shows your average blood sugar over the past two to three months. The American Diabetes Association uses these cut-offs: 5.7% to 6.4% is prediabetes, and 6.5% or higher is diabetes. Plenty of people in the prediabetes range have no idea.
Why it matters for the baby: a 2025 analysis of 202 studies covering about 56 million mother-child pairs found that diabetes in pregnancy was linked to roughly 25% to 30% higher relative risk of autism and ADHD, with a stronger link for diabetes that started before pregnancy. These are associations, and the absolute increase for any one child is small. But blood sugar is one of the few things you can move a lot in 90 days.
Ask for an A1c if you carry extra weight, have had gestational diabetes, have PCOS, have diabetes in the family, have high blood pressure or heart disease, or are of South Asian, Black, Hispanic, Indigenous or East Asian heritage.
Vitamin D, B12 and STI tests
Vitamin D. The US recommended amount in pregnancy is 600 IU a day, with an upper limit of 4,000 IU. Darker skin, little sun and obesity raise the chance of a low level. Two US studies hint that levels in early pregnancy may matter most, which is a reason to ask now. More in vitamin D before pregnancy.
B12. The NIH notes that B12 deficiency in pregnancy might cause neural tube defects and developmental delays. Vegans, vegetarians and people on metformin should ask for a test. Correcting a real deficiency matters; extra B12 on top of normal levels isn't a brain booster.
STIs. The CDC recommends testing all pregnant women for HIV, syphilis and hepatitis B at the first prenatal visit, with hepatitis C screening in each pregnancy and chlamydia and gonorrhea testing for women under 25 or at higher risk. There's a good case for testing both partners before you conceive. Congenital syphilis has risen in the US for 12 years in a row, with nearly 4,000 reported cases in 2024 (provisional data). It's preventable with testing and treatment.
Beyond blood tests: the rest of the visit
The same appointment should cover a few things that aren't blood tests:
- Blood pressure. High blood pressure before pregnancy raises the risk of preeclampsia. The CDC advises sorting out treatment and reviewing medicines before pregnancy.
- Every medicine and supplement. Bring the bottles or photos of the labels. Isotretinoin, valproate and weight-loss injections such as semaglutide need a plan months ahead. Never stop a seizure medicine on your own.
- Your folic acid dose. 400 mcg a day is standard. Some people need more.
- A dental cleaning. Easier to schedule before pregnancy.
- Chronic conditions like asthma, depression or epilepsy, which may need a plan.
Test, don't guess. Fix what's low; more than enough doesn't help. Write your results down so you can track them, and ask your partner to book their own check-up and STI tests.
Do this
- Book a preconception visit for about three months before you hope to start trying.
- Ask for TSH, ferritin and A1c by name, and B12 if you're vegan, vegetarian or on metformin.
- Photograph every medicine, supplement and cream and bring the photos.
- Ask whether a vitamin D test makes sense for you.
- Ask your partner to book their own check-up and STI tests.
When to ask your doctor
Check with your doctor or midwife first if…
- You take isotretinoin, valproate or any seizure medicine, or a weight-loss injection such as semaglutide: talk to your prescriber well before trying.
- You already have diabetes, a thyroid condition or high blood pressure: ask what targets your doctor wants before you conceive.
- You're vegan or take metformin: ask specifically for a B12 test.
Call your doctor now if…
- You're pregnant and have vaginal bleeding or fluid leaking: call your doctor or 911 now.
- You have a severe headache that won't go away or vision changes in pregnancy: call your doctor or 911 now.
This page is general information, not medical advice. Every pregnancy and every child is different. Ask your doctor, midwife or pediatrician before changing supplements, diet or care.
Grow a Genius
In the book: Chapter 6: The Preconception Check-Up
Grow a Genius includes a printable take-along checklist for this visit, with a column for your results, plus a matching list for your partner in The Dad Factor: 90-Day Plan.
- The 7 Genius Builders, stage by stage
- 16 printable guides, including the Prenatal Label Decoder
- Built on 500+ sources from 35+ countries
- 90-day Double Guarantee
People also ask
Does insurance cover preconception blood tests?
Coverage depends on your plan and why the test is ordered. Thyroid, iron, blood sugar and STI tests are standard tests your doctor can order. Carrier screening varies the most, so ask what it covers and what your insurance pays before you book.
Should my partner get tested before we try?
Yes, at least for STIs. Some infections pass to the baby, and testing both partners before conception means treatment can happen first. Your partner should also book a check-up to review medicines, smoking and alcohol, since sperm take about 64 to 74 days to develop.
What is a good ferritin level before pregnancy?
Your doctor will interpret your result. In one Irish study, mothers who weren't anemic but had ferritin under 30 µg/L at 15 weeks had babies with lower cord-blood iron. That's why ferritin, not just hemoglobin, is worth asking for.
Do I need genetic carrier screening?
It's optional. Carriers are usually healthy; what matters is whether both partners carry a change for the same condition. Doing it before pregnancy gives you the most options and time to talk with a genetic counselor.