A vitamin deficiency often creeps in unnoticed. Symptoms like ongoing fatigue, hair loss, tingling or a pale skin can point to a lack of a vitamin or mineral, but they can also mean something else. A blood test is the only way to know for certain which value is genuinely too low. In this article you will read which symptoms match which vitamin, which deficiencies are most common, and when testing is and is not worthwhile.
My advice up front: do not start taking supplements on a hunch. Measure first, then act.
What is a vitamin deficiency?
A vitamin deficiency means your body structurally takes in or absorbs too little of a particular vitamin to function well. Vitamins and minerals drive countless processes, from your energy balance to blood formation and nerves. A deficiency usually builds up slowly, which is why the first symptoms are easy to miss.
The difference with minerals is small in practice. Vitamins are organic compounds (such as vitamin D and B12), minerals are inorganic (such as magnesium and iron). For both, too little causes symptoms, and you often notice it only once the shortage has lasted a while.
What are the symptoms of a vitamin deficiency?
The symptoms of a vitamin deficiency depend on which vitamin you lack. Common complaints are ongoing fatigue, hair loss, a pale skin, tingling in hands or feet, muscle cramps, mouth ulcers and low mood. Because these complaints are broad, they do not point to one specific cause on their own.
What makes it tricky: fatigue can just as easily come from your thyroid, your iron or your sleep. That is why the pattern matters. Tingling together with fatigue and concentration problems fits a vitamin B12 deficiency better than fatigue alone.
- Fatigue and low energy: can relate to vitamin B12, vitamin D or iron
- Tingling or numbness: fits a vitamin B12 deficiency
- Muscle cramps and trembling: can point to too little magnesium
- Hair loss and brittle nails: often relate to iron, vitamin D or folate
- Pale skin and shortness of breath: can fit anaemia from iron, B12 or folate
- Bone pain and muscle weakness: are classic signals of a vitamin D deficiency
Which vitamin deficiencies are most common?
In the Netherlands four deficiencies are by far the most common: vitamin D, vitamin B12, folate and iron (measured through ferritin). Magnesium follows at some distance. These nutrients come from food and, for vitamin D, mainly from sunlight, which makes the risk groups easy to identify.
- Vitamin D: at the end of winter 7 to 26 percent of people in the Netherlands have a deficiency. You mainly produce it in the skin under the influence of sunlight. Read more about vitamin D deficiency and its symptoms and how serious a deficiency is.
- Vitamin B12: a risk for vegans, vegetarians and older adults, and with stomach or bowel problems. See the risk groups for a vitamin B12 deficiency and read how to correct vitamin B12.
- Folate (vitamin B11): important when trying to conceive and in the first weeks of pregnancy. The Netherlands Nutrition Centre then advises 400 micrograms a day. Read more about folate deficiency and pregnancy.
- Iron: women with heavy periods are particularly at risk. Iron is measured through your ferritin.
- Magnesium: a shortage can relate to muscle cramps, fatigue and a restless feeling. Read more about magnesium deficiency and its symptoms.
- B vitamins: vitamin B12 and folate belong to the vitamin B complex.
How do you know which vitamin you are short of?
You cannot tell from your symptoms alone which vitamin you lack, because many symptoms overlap. A targeted blood value gives clarity. The table below links common complaints to the vitamin or mineral that may be behind them, and to the value you would check.
| Complaint | Possible vitamin or mineral | Blood value to check |
|---|---|---|
| Ongoing fatigue | Vitamin B12, vitamin D, iron | Vitamin B12, vitamin D, ferritin |
| Tingling in hands or feet | Vitamin B12 | Vitamin B12 |
| Muscle cramps and trembling | Magnesium | Magnesium |
| Hair loss and brittle nails | Iron, vitamin D, folate | Ferritin, vitamin D, folate |
| Pale skin and shortness of breath | Iron, vitamin B12, folate | Ferritin, vitamin B12, folate |
| Bone pain and muscle weakness | Vitamin D | Vitamin D |
| Mouth ulcers and cracked mouth corners | Vitamin B12, folate, iron | Vitamin B12, folate, ferritin |
| Low mood and concentration problems | Vitamin D, vitamin B12 | Vitamin D, vitamin B12 |
An abnormal value is not a diagnosis. It shows where something may be going on, so that you and your GP can look further in a targeted way.
Can you test for a vitamin deficiency with a blood test?
Yes, a blood test is the most reliable way to establish a vitamin deficiency. In the laboratory the amount of a vitamin or mineral in your blood is measured. For vitamin D, vitamin B12, folate, iron and magnesium there are clear, validated tests.
Worth knowing: GPs and scientists point out that randomly testing many vitamins often yields little. Testing is mainly worthwhile if you have symptoms or belong to a risk group. Think of a plant-based diet, little sunlight, older age, a wish to conceive or stomach and bowel complaints.
Less useful is having your entire vitamin panel measured without symptoms or risk factors. A targeted test based on your situation gives more value than a broad screening. Want to decide what to test yourself? With a custom blood test you choose exactly the values that fit your complaints, or you pick a ready-made B-vitamins test.
What can you do about a vitamin deficiency?
With a confirmed deficiency you usually start at the cause: your diet, your lifestyle and possibly a supplement. Which approach fits depends on which vitamin is low and how large the shortage is. Discuss this with your GP, certainly if the deficiency is substantial.
- Diet: oily fish, eggs, meat, dairy, legumes and green leafy vegetables provide most vitamins and minerals.
- Sunlight: for vitamin D, being outside is the main source. In the Dutch winter that is often not enough.
- Supplements: the Health Council advises some groups (such as women over 50 and men over 70) to take vitamin D. Read how much vitamin D per day you need. For other deficiencies a supplement may be needed on your doctor's advice.
- Follow-up: after a while you can have your value measured again to see whether the approach is working.
Frequently asked questions
How quickly do you notice a vitamin deficiency?
That varies per vitamin. A deficiency usually builds up over weeks to months. As a result the first symptoms are often vague, such as a little more fatigue than normal.
Which vitamin most often causes fatigue?
Fatigue belongs to several deficiencies. Vitamin B12, vitamin D and iron are the most common culprits. A blood value shows which of the three is involved.
Do I need to fast for a vitamin test?
For most vitamin tests you do not need to fast. If your iron or glucose is measured alongside, fasting blood may be requested. Follow the advice that comes with your test.
The bottom line
My advice: do not let online symptom lists worry you. Fatigue or hair loss says little on its own. If you have symptoms or belong to a risk group, have the values that matter for your situation measured in a targeted way. Every blood test result at Vitalcheck includes a professional assessment by a BIG-registered doctor. A blood value is not a diagnosis: always discuss symptoms and treatment decisions with your GP.
References
- Health Council of the Netherlands. Dietary reference values for vitamins and minerals. 2018.
- RIVM. At most a quarter of the Dutch population has a vitamin D deficiency in winter. 2023.
- Thuisarts.nl / NHG. Vitamin B12: what if you have too little? Accessed 2026.
- Netherlands Nutrition Centre. Folic acid and pregnancy. Accessed 2026.
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