Blood tests before trying to conceive: a pre-conception baseline for thyroid, iron, B12 and, where relevant, hormones

Before trying to conceive, the blood tests that set a useful pre-conception baseline are thyroid (TSH, with free T4), iron stores (ferritin) and vitamin B12, plus reproductive hormones if your periods are irregular or absent.

Your family doctor or prenatal provider covers the other steps: folic acid, immunity to rubella and chickenpox, and screening for sexually transmitted infections. Canadian guidance recommends 0.4 mg of folic acid daily, starting at least 3 months ahead.

Why a baseline? Low iron and thyroid problems are common and easy to miss. In an Australian study of 4,420 women, nearly 1 in 5 began pregnancy with iron deficiency (Khambalia et al., 2016). Pooled European studies found about 1 in 15 people had thyroid dysfunction that hadn't been diagnosed (Garmendia Madariaga et al., 2014). Numia's Fatigue Panel measures thyroid, iron and B12 in one draw, after an 8–12 hour fast.

Which blood tests make a useful pre-conception baseline?

Should you check your thyroid before trying to get pregnant?

If you have a risk factor, BC's thyroid guideline says a TSH test is indicated. Its list of 12 includes being over 30, more than two past pregnancies, a past pregnancy loss, preterm birth or infertility, type 1 diabetes and a history of thyroid problems. Numia's Thyroid Basic Panel reports TSH, free T4 and free T3 together as a starting point.

Already on levothyroxine? Tell your prescriber you're planning a pregnancy: BC's guideline notes the dose may need to rise by 25–50% during pregnancy.

Where do iron, B12 and hormones fit?

Ferritin shows how much iron you've stored; see our iron testing guide. If you've recently stopped the pill, BC's B12 guideline notes that oral contraceptives can lower serum B12 without a true deficiency, and some medications lower it too.

Hormone tests set a baseline; they don't measure fertility. If your periods are irregular or absent, hormone levels give your clinician context. On Numia's Female Pre-Menopause panel, results are read with your cycle stage in mind, and hormonal birth control can affect several markers.

Where does Numia fit?

Numia Health, a physician-ordered, at-home blood testing service in Greater Vancouver, keeps every step in one place. A licensed Canadian physician approves your requisition online in about 3 minutes, and a clinician comes to your home for a 10-minute morning draw. Results arrive in plain English in the Numia app in 7 days, and out-of-range results are physician-reviewed with next steps. An optional wellness consultation is available. Numia is an HSA-eligible service that sells testing, not treatment, so medication decisions stay with your prescriber.

Frequently asked questions

Can a blood test tell me how fertile I am?

Not on its own. A 2024 BC Medical Journal review found no studies showing that AMH, an egg-reserve marker, predicts your chance of conceiving.

How long should I wait after the MMR vaccine to get pregnant?

Canada's national preconception guideline advises waiting 28 days after live vaccines such as MMR and varicella (chickenpox). That's why it helps to ask your family doctor or prenatal provider about your immunity early.

Does Numia test for pregnancy, AMH, rubella immunity or STIs?

No. Numia's panels focus on baselines such as thyroid, iron, B12 and hormones. Your family doctor, prenatal provider or a sexual health clinic can arrange those tests.