B-group vitamins: energy, nerves, blood formation, and symptoms of deficiency

02. 09. 2026

EDUCATIONAL ARTICLE · 03 / 08 · B vitamins

B Vitamins: Energy, Nervous System, Blood Formation and Signs of Deficiency

The B group consists of eight vitamins with different roles. This overview helps you compare their sources, understand B-complex supplements and recognise when it may be useful to assess the intake or absorption of a particular nutrient.

Author: Ing. František Kokoš · Updated: 6 October 2026

01 · Eight vitamins, eight distinct nutrients

B vitamins: basic differences and examples of food sources

Vitamin

Role in the body

Food sources

B1 – thiamin

Using energy from nutrients; nervous system function.

Pulses, wholegrain bread, nuts and pork.

B2 – riboflavin

Energy metabolism; skin and mucous membranes.

Milk, yoghurt, eggs and mushrooms.

B3 – niacin

Energy metabolism; nervous system and skin.

Meat, fish, eggs and cereals.

B5 – pantothenic acid

Nutrient metabolism.

Poultry, eggs, mushrooms and avocado.

B6 – a group of compounds including pyridoxine

Amino acid metabolism and haemoglobin formation.

Poultry, fish, chickpeas and bananas.

B7 – biotin

Processing fats, carbohydrates and amino acids.

Cooked eggs, nuts, seeds and meat.

B9 – folates

DNA synthesis, cell division and blood formation.

Leafy vegetables, broccoli and pulses.

B12 – cobalamins

Nervous system function, DNA synthesis and red blood cells.

Animal foods and suitable fortified foods.

Folates are a broader group of compounds; folic acid is one form used in supplements and fortified foods. Similarly, vitamin B3 includes both nicotinic acid and nicotinamide.

Source: NHS – B vitamins and folic acid.

Source: NIH ODS – biotin.

Source: NIH ODS – folate.

↑ Back to contents

02 · Will a B complex give you more energy?

B vitamins help the body process nutrients. They do not themselves provide calories or replace food, sleep or rest.

For example, vitamin B12 supplementation has not been shown to improve athletic performance or endurance when B12 status is adequate. Correcting a deficiency is a different situation from adding a dose for someone who already has enough of the nutrient.

Source: NIH ODS – B12, energy and endurance.

If you are dealing with persistent fatigue, continue with Energy and Less Fatigue: Why Do We Lack Energy?

↑ Back to contents

03 · Who is at greater risk of deficiency?

Situations in which a particular nutrient needs attention

Situation

What to consider

Vegan diet

Ensure a reliable source of B12 from suitable fortified foods or a supplement.

Older age or impaired absorption

Assess B12 absorption and status; dietary intake alone may not be sufficient.

Stomach or intestinal surgery

Follow an individual plan for monitoring and supplementation.

Metformin and certain medicines that reduce stomach acid

These can affect B12 status. Do not stop prescribed medicines on your own.

Pregnancy and planning a pregnancy

Address folic acid early and ensure adequate intake of other nutrients.

A highly restricted diet or excessive alcohol intake

Assess overall nutrition and, depending on the circumstances, the risk of B1 and other vitamin deficiencies.

Source: NIH ODS – groups at risk of B12 deficiency.

Source: NIH ODS – folate and pregnancy.

When planning a pregnancy, do not wait for a positive test: discuss folic acid with your healthcare professional beforehand.

↑ Back to contents

04 · Symptoms overlap: finding the cause matters

Fatigue, weakness and changes to the tongue or corners of the mouth can accompany certain vitamin deficiencies, but they do not establish a diagnosis. Tingling can be associated with B12 deficiency, other conditions or excessive B6 intake.

B12 deficiency can damage the nervous system even without anaemia. Do not delay medical assessment if you have persistent tingling, altered sensation, unsteadiness when walking or memory changes.

Before a consultation, note when symptoms began, any dietary restrictions, your medicines and all supplements, including their doses. The choice of tests depends on the individual situation.

Source: NIH ODS – B12 deficiency.

Source: NIH ODS – risks of excessive B6 intake.

↑ Back to contents

05 · B complex or an individual vitamin?

Choosing according to need

Option

What to check

B-complex supplement

Which vitamins it contains and their daily amounts. The name does not mean that every product has the same formula.

Individual vitamin

Is there a reason to supplement this particular nutrient? If a deficiency has been confirmed, follow the treatment plan.

Several combination supplements

Add up overlapping ingredients, such as B6 in a B complex, a magnesium supplement and a multivitamin.

A varied diet with no identified deficiency

Consider whether an additional supplement addresses a specific need.

A nutrient requirement, the daily amount in a product and an upper intake limit are different concepts. Compare the amount per recommended daily serving, and add up overlapping ingredients across all supplements.

↑ Back to contents

06 · Water-soluble does not mean unlimited doses

B6 and nerves

Long-term excessive intake can damage peripheral nerves. Check the total B6 from all supplements, even when the products are marketed for different purposes.

B3 and the form used

At higher doses, nicotinic acid can cause skin flushing. High doses can also have more serious adverse effects; medical use requires a doctor's supervision.

B9 and B12 deficiency

High folate intake can correct the anaemia caused by B12 deficiency while leaving nerve damage unaddressed. Folate therefore does not replace treatment for B12 deficiency.

Source: EFSA – assessment of the upper intake level for vitamin B6.

Source: NHS – niacin.

Source: NIH ODS – folate and B12.

↑ Back to contents

07 · Tell your healthcare team about biotin before a blood test

Biotin can interfere with certain laboratory methods and cause falsely high or low results. Examples include some hormone tests and cardiac markers.

Tell your doctor and the laboratory the supplement name, biotin dose and time of your last dose. They will decide whether a pause is needed based on the specific test and product.

Source: NIH ODS – biotin and laboratory tests.

For more context on beauty supplements, see Skin, Hair and Nails.

↑ Back to contents

08 · Frequently asked questions

How many B vitamins are there?

Eight: B1, B2, B3, B5, B6, B7, B9 and B12.

Why are numbers such as B4 missing?

Historical names also included substances that are no longer classified as separate B vitamins.

Does everyone need a B complex?

Not automatically. Diet, absorption, health circumstances and individual needs matter.

Can B12 deficiency occur without anaemia?

Yes. Neurological symptoms can occur even without anaemia.

Is a higher B6 dose better for nerves?

No. Excessive B6 intake can damage nerves.

Is biotin also found in combination supplements?

Yes. It may be included in B complexes, beauty supplements and some collagen products. Check the label.

↑ Back to contents