Folate deficiency: symptoms and when to test

You usually recognise a folate deficiency by ongoing fatigue, pale skin, irritability and sometimes a sore, smooth tongue. In practice I see that many women only notice the deficiency once symptoms have been there for a while. A blood test then gives you clarity and direction.

Folate, also known as vitamin B11, plays an important role in producing red blood cells and in cell division. That is exactly why it gets so much attention around a wish to conceive.

In this article I share what the symptoms can look like, when testing may make sense, and why folate and vitamin B12 are so closely connected.

What are the symptoms of a folate deficiency?

The symptoms of a folate deficiency often resemble those of anaemia: fatigue, pale skin, shortness of breath on exertion and sometimes palpitations. You may also notice a sore or smooth tongue, irritability and trouble concentrating. Because the complaints usually develop gradually, they are easily overlooked.

Folate is needed to produce healthy, normally sized red blood cells. With a prolonged deficiency those cells can become too large, which may cause a form of anaemia known as megaloblastic anaemia.

Common signs that women describe include:

• Fatigue and listlessness that do not disappear after rest.
• Pale or slightly yellowish skin.
• A sore, red or smooth tongue and sometimes mouth ulcers.
• Irritability, low mood or trouble concentrating.
• Breathlessness or palpitations on light exertion.

Important to know: these complaints are not specific to folate alone.

They may just as easily point to an iron or vitamin B12 deficiency, or to something entirely different. That is why only a blood test gives real clarity about your folate level. If you want a broader look at your vitamin status, read our overview of which vitamins and minerals women can have tested.

When should you have folate tested?

A folate test can make sense if you are tired for a long time, follow a one-sided or plant-based diet, are trying to conceive, or if anaemia has been found without a clear cause. Bowel conditions or certain medicines can also reduce how well you absorb it. A test then offers guidance.

When measuring folate there are roughly two types of tests, and the difference is worth knowing.

• Serum folate measures the amount of folate circulating in your blood at that moment. This value fluctuates strongly with what you have eaten over the past few days.
• RBC folate (folate inside the red blood cells) reflects your stores over a longer period, roughly the past few months. It therefore gives a more stable picture of your status.

In practice serum folate is often measured first, because it is simple and widely available. In case of doubt a doctor may consider an additional RBC folate test.

If you want to understand what an individual value means, you can find background on our folate biomarker page. A result is always interpreted alongside your symptoms and the rest of your blood picture, never as a stand-alone number.

Folate and vitamin B12: why are they connected?

Folate and vitamin B12 work closely together in producing red blood cells and in keeping your nervous system functioning. That makes them an important duo. The risk lies here: a high intake of folate can hide the anaemia of a B12 deficiency, while damage to the nerves may quietly continue.

This phenomenon is called masking, and it is exactly why folate and B12 are best assessed together.

In the blood picture, both a folate and a B12 deficiency often cause enlarged red blood cells. If you take folate, that can partly normalise the blood values, making it seem as though everything is fine. The underlying B12 problems, such as tingling or numbness in hands and feet, may then go unnoticed.

My advice is therefore not to simply start taking high doses of folate for fatigue without knowing your B12. Have them assessed together.

If you want to go deeper into the B12 side, read our article about a vitamin B12 deficiency and how to have it tested. Both vitamins also appear in our B-vitamins blood test, which looks at your B vitamins together.

Folate when trying to conceive and during pregnancy

Around a wish to conceive, folate receives extra attention because it plays a role in the early development of a baby's nervous system. As standard advice, the Dutch Health Council recommends that women trying to conceive take 400 micrograms of folic acid daily, from roughly four weeks before conception until about ten weeks of pregnancy.

That timing is no coincidence.

The neural tube, from which the brain and spinal cord later develop, closes very early in pregnancy, often before a woman knows she is pregnant. That is why bodies such as the Health Council and the RIVM advise starting a folate supplement well before conception, so that stores are sufficient when it matters most.

This is general information and not a replacement for personal advice. Exactly how much you need, and whether a higher dose is appropriate, is something you discuss with your GP or midwife.

A blood test is not a required part of this standard advice; supplements are usually recommended regardless of your result. Even so, some women choose to map their broader status before they want to become pregnant. If you want to know which values may be relevant, read our overview of which blood test may suit a wish to conceive or look at our prenatal essentials blood test.

Frequently asked questions

How long does it take to replenish a folate deficiency?

This differs from person to person and depends on the cause and the approach. With sufficient intake, blood values often recover within a few weeks to months. A doctor may advise testing again later to see how your values are developing.

Can I correct a folate deficiency through diet?

Folate occurs naturally in green leafy vegetables, legumes, wholegrain products and citrus fruit, among others. For many women a varied diet helps keep their status up. Around a wish to conceive a supplement is usually also recommended, because diet alone is often not enough.

Is a high folate level harmful?

A raised value from food is usually not a problem. However, a high intake from supplements can, as described earlier, mask an underlying vitamin B12 deficiency. That is why it is wise to assess folate and B12 together and to discuss doses with your GP.

Sources

1. Health Council of the Netherlands (Gezondheidsraad). Advice on preconception and folate: recommendation of 400 micrograms per day around conception (Gezondheidsraad).
2. RIVM. Nutrition advice and folate around pregnancy and conception (RIVM, accessed 2026).
3. Cochrane Database of Systematic Reviews. Folate supplementation before and during pregnancy for preventing neural tube defects (Cochrane review).
4. Dutch College of General Practitioners (NHG). Guideline and background on anaemia and vitamin deficiencies (NHG).

Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.