You are standing in the pharmacy in front of the ovulation tests and think: would I actually know where my body stands? Maybe you have been trying for a few months, maybe you want insight before you begin. In both cases a blood test lets you act more precisely, because good preparation starts before conception.
My view: a preconception blood test does not belong in the panic-reaction category, but in the smart-preparation one. The more you know about your hormones and nutritional status, the less you have to guess. In this article we walk through all the relevant blood values, when to measure them, and what the results tell you.
Why have blood tested when trying to conceive?
A preconception blood test is not an obligation and not a cause for worry. It is a proactive step that helps you spot any deficiencies or hormonal imbalances early, so you can address them before you become pregnant. Some things, such as low folate or suboptimal thyroid function, are easy to adjust if you catch them in time. Other values, such as AMH, give insight into your fertility status, so you can make considered choices about timing.
Which value when? An overview
Not all blood values are measured at the same moment. The table below shows what each marker tells you and when to test it, so you get a complete picture in as few draws as possible.
| Blood value | What it tells you | Best time to test |
|---|---|---|
| AMH | Indication of your egg reserve | Any point in your cycle |
| FSH and LH | Signalling of egg maturation and ovulation | Cycle day 2-4 |
| Estradiol | Basal hormone production | Cycle day 2-5 |
| Progesterone | Confirmation of ovulation | Cycle day 19-22 (28-day cycle) |
| TSH | Thyroid function | Any point in your cycle |
| Ferritin | Your iron stores | Any point in your cycle |
| Vitamin D, B12, folate | Nutritional status for a healthy start | Any point in your cycle |
AMH: your ovarian reserve
AMH (anti-Müllerian hormone) gives an indication of your egg reserve: the number of eggs you have left. AMH is produced by small follicles in your ovaries and declines gradually with age. A few nuances are essential:
- Quantity, not quality: AMH says something about how many eggs you have, not how good they are. Quality depends mainly on your age.
- Not a fertility test: a low AMH does not mean you cannot conceive. It can mean your fertile window is shorter.
- Flexible timing: AMH can be measured at any point in your cycle.
- Pill use: the value can be temporarily lowered after stopping the pill. Preferably wait two to three months.
Especially if you are over 30, have a family history of early menopause, or want to know whether there is time pressure, AMH is one of the most informative markers to test.
FSH and LH: the control of your cycle
FSH and LH together regulate the maturation of eggs and ovulation. For representative values, measure them on cycle day 2, 3 or 4, when they are most stable. A raised FSH (above 10-12 IU/L on day 3) can point to a reduced egg reserve. In PCOS, LH is often higher than FSH, with an LH/FSH ratio of 2:1 or higher, while normally it is around 1:1. The LH surge just before ovulation can also be measured at home with ovulation tests.
Estradiol and progesterone: confirming the cycle
Estradiol (E2) on cycle day 2-5 reflects your basal hormone production and is important for building the uterine lining. A high estradiol early in the cycle can, like a raised FSH, point to a declining reserve.
Progesterone is measured in the luteal phase, around cycle day 19-22 for a 28-day cycle. A sufficiently high value (usually above 25-30 nmol/L) confirms that ovulation occurred. A low value can point to a cycle without ovulation or an insufficient luteal phase; both are treatable in consultation with a doctor. Adjust the timing if your cycle is shorter or longer than 28 days: ideally measure seven days after presumed ovulation.
Thyroid function: essential and often forgotten
Your thyroid plays a larger role in fertility than many women realise. TSH is the key screening marker and can be measured any time. For women trying to conceive, the ideal values are stricter than the standard reference range: international guidelines advise a TSH below 2.5 mIU/L, while labs often treat up to 4.0 or higher as normal. A subclinically raised TSH can affect ovulation, the risk of miscarriage, and the baby's early brain development, which in the first weeks depends entirely on the mother's thyroid hormones.
If TSH is abnormal, further investigation with free T4 is useful. Always discuss an abnormal TSH with a doctor if you want to become pregnant; treatment is usually simple and effective.
Ferritin and iron: build a reserve
During pregnancy your blood volume rises by about 50%, which requires a lot of iron. Starting with empty reserves increases the risk of anemia and fatigue. Ferritin gives the most reliable picture of your iron stores; aim for at least 40-50 µg/L when trying to conceive. Replenishing takes three to six months, so start in time. If you wish, also measure your hemoglobin, which shows whether you currently have enough red blood cells.
Vitamin D, B12 and folate
Vitamin D is involved in implantation and placental development. In the Netherlands a large share of the population has a suboptimal level, especially in winter. The Gezondheidsraad advises women trying to conceive to take 10 µg of vitamin D daily.
Folate is crucial for the early development of the nervous system. Thuisarts.nl advises starting folate before conception, because a deficiency in the first weeks raises the risk of neural tube defects. Vitamin B12 works closely with it and is mainly a concern if you eat few animal products.
Frequently asked questions
When to start testing?
Ideally three to six months before you actively start trying. That gives time to top up deficiencies and optimise thyroid function. But even if you are already trying, testing is valuable: there is no wrong moment to gain more insight.
What if AMH is low?
A low AMH can feel worrying, but put it in perspective. AMH says something about the number of eggs, not their quality. Women with a low AMH still conceive naturally. Always discuss your value with a doctor or fertility specialist, who can place it in the context of your age and situation. A low AMH is not a diagnosis of infertility.
How long to try before testing?
The NHG guideline and Thuisarts.nl use as a rule: under 35, further investigation after twelve months of actively trying; over 35, after six months. With risk factors such as an irregular cycle or endometriosis you can consult a doctor sooner. A preconception blood test can always be done, even before you begin.
A complete picture in one go
If you want the key hormones and nutrients measured together, the Fertility Assessment brings them into a single draw. For a broader nutritional base, look at the Prenatal Essentials, and for a wider hormone screening the Hormones Women panel.
Read on? See fertility testing: what you need to know, our explainer on AMH value by age, and the pillar hormone testing in women.
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