The vitamin B complex is a group of eight B vitamins that together support your energy balance, nervous system and blood formation. The best known are vitamin B12 and folate (B11). This article is part of our overview of vitamin deficiency. Below you read which B vitamins there are, what they do and when a deficiency matters.
Which B vitamins are in the B complex?
The B complex includes eight water-soluble vitamins. They often work together, but each has its own role.
- B1 (thiamine) - energy from carbohydrates, nerve function
- B2 (riboflavin) - energy metabolism, skin and eyes
- B3 (niacin) - energy and cell repair
- B5 (pantothenic acid) - production of hormones and fatty acids
- B6 (pyridoxine) - protein metabolism, neurotransmitter production
- B7 (biotin) - skin, hair and metabolism
- B11 (folate) - cell division and blood formation
- B12 (cobalamin) - nervous system and red blood cells
What does the vitamin B complex do?
The B vitamins together play a central role in your energy metabolism: they help your body extract energy from food. They are also needed for your nervous system, your blood formation and cell repair. A good intake supports your energy level, but does not resolve fatigue on its own if another cause is at play.
When is there a B vitamin deficiency?
You get most B vitamins amply from a varied diet. Two stand out when it comes to deficiencies: vitamin B12 and folate.
- A vitamin B12 deficiency occurs in vegans, older adults and with stomach or bowel problems.
- A folate deficiency matters mainly around pregnancy and with a one-sided diet.
Because B12 and folate can mask each other in symptoms and in the blood picture, they are often assessed together.
Does a B complex supplement make sense?
For most people with a varied diet, a general B complex is not needed. It can be worthwhile with a plant-based diet, a confirmed deficiency or on your doctor's advice. If you take a supplement on a hunch, you do not know whether you really need it. Targeted testing gives more clarity than a broad supplement.
Where are B vitamins found?
- Meat, fish, eggs and dairy - rich in B12 and other B vitamins
- Wholegrain products and legumes - B1, B3, B6, folate
- Green leafy vegetables - folate
- Nuts and seeds - B5, B6, biotin
Testing your B vitamins
Want to know whether your B12 and folate are at the right level? A B vitamins test measures the key values, or you build a custom blood test. 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.
- Netherlands Nutrition Centre. Vitamin B12 and folate. Accessed 2026.
- Thuisarts.nl / NHG. Vitamin B12. Accessed 2026.
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