Vitamin B7 (Biotin)

Biotin (vitamin B7, sometimes called vitamin H) is best known for its association with hair, skin and nails. It appears in many "beauty" supplements, often at doses far higher than those found naturally in food.

What’s less widely understood is that biotin is first and foremost an essential vitamin involved in everyday metabolism, and that true deficiency is uncommon in the UK when someone eats a varied diet. This does not mean biotin has no value, but it does mean many claims around supplements go further than the evidence allows.

This article explains what biotin does, who may be at risk of low levels, what research says about supplements, and one key safety issue pharmacy customers should be aware of: biotin can interfere with some blood test results.

What is vitamin B7 (biotin)?

Biotin is a water-soluble B vitamin. Unlike fat-soluble vitamins, the body does not store much of it, so regular intake from food is needed. Some biotin is also produced by gut bacteria, but diet remains the main source for most people.

In simple terms, biotin helps certain enzymes work properly. These enzymes are involved in how the body processes fats, carbohydrates and proteins. Because small amounts of biotin are found in many foods, most people meet their needs without realising it.

What does biotin do in the body?

Biotin supports normal metabolism by helping the body release energy from food. Without enough biotin, some of these processes work less efficiently, which can contribute to symptoms over time.

It also contributes to the maintenance of normal hair and skin, a claim recognised by European regulators. This means biotin helps keep tissues functioning normally; it does not mean it enhances appearance beyond normal levels.

Finally, biotin contributes to normal nervous system function. Severe deficiency can affect nerves and mood, though this is rare in the general population.

Food sources of biotin

Biotin is widely distributed across foods, and normal cooking does not usually destroy it. Cooked eggs are a useful example, as heat disables the raw egg white protein that can otherwise bind biotin.

Common UK dietary sources include:

Eggs (mainly the yolk)
Nuts and seeds (such as almonds, peanuts and sunflower seeds)
Legumes (beans, lentils and soya)
Fish, including salmon
Mushrooms and sweet potatoes

For most people eating a varied diet, this is enough to cover daily needs without supplements.

How much biotin do you need?

The UK does not set a specific Reference Nutrient Intake for biotin, but international guidance places typical "adequate intake" levels for adults in the tens of micrograms per day. Most diets comfortably reach this level.

Many hair and nail supplements contain 5,000–10,000 micrograms (5–10 mg). These doses are far above nutritional requirements. While not usually toxic, they are relevant to safety because higher doses are more likely to interfere with certain blood tests.

Who might be at risk of low biotin?

Biotin deficiency is rare, but it can occur when there is an underlying issue. People who may be at higher risk include those with conditions or circumstances that affect absorption or metabolism.

This includes people taking some long-term anti-seizure medicines, those with digestive conditions such as inflammatory bowel disease, people with alcohol dependence, and individuals with rare inherited conditions affecting biotin recycling. Pregnancy and breastfeeding may also increase biotin requirements slightly, though routine high-dose supplementation is not generally advised without professional input.

If deficiency is suspected, identifying and addressing the underlying cause is usually more important than self-supplementing.

Nature's Bounty Beauty Complex with Biotin 60 Caplets

Biotin supplements: do they actually help?

Biotin supplements are heavily marketed, but evidence of benefit depends on the situation.

For hair growth, good-quality evidence in people who already have enough biotin is limited. Where biotin clearly helps, it is usually correcting a genuine deficiency or a specific medical condition. Hair loss is far more often linked to other causes such as iron deficiency, thyroid disorders, hormonal changes, stress, recent illness, or pattern hair loss.

For brittle nails, small studies suggest some people may improve after several months of supplementation. However, these studies were limited and did not always confirm biotin deficiency beforehand, so it is unclear who is most likely to benefit.

For skin, biotin deficiency can cause skin problems, but there is little evidence that high-dose biotin improves skin appearance in people who already have adequate intake.

A balanced summary is: biotin is essential for normal hair, skin and nails, but extra biotin does not reliably improve them if levels are already sufficient.

Safety, side effects and interactions

Blood test interference

The most important safety issue with biotin supplements is their effect on certain blood tests. Some laboratory tests rely on biotin as part of how results are measured. High levels of biotin in the blood can interfere with this process, leading to misleading results.

Tests most commonly affected include thyroid function tests and some cardiac tests used when doctors assess possible heart attacks. This interference has been reported at doses as low as 5 mg (5,000 micrograms), which are common in hair and nail products.

Practical advice for customers:

Tell healthcare professionals if you take biotin supplements.
Follow advice on stopping biotin before blood tests, often at least 48 hours.

General safety

Biotin itself is usually well tolerated, as excess is passed out in urine. Side effects are uncommon. However, supplements should not replace investigation of symptoms such as hair loss or fatigue.

Pharmacist comment

As Alessandro Grenci, Superintendent Pharmacist, explains:

"Most people in the UK get enough biotin from food. The bigger issue I see is customers assuming hair loss means biotin deficiency, when there are many other causes. High-dose biotin can also interfere with blood tests, including thyroid tests, so it’s important to tell your clinician if you’re taking it."

Should you take a biotin supplement?

Biotin supplementation may be reasonable when there is a clear reason, such as confirmed deficiency, certain medical conditions affecting absorption, or specialist advice for brittle nail syndrome. For most people eating a varied diet, routine supplementation is unlikely to add benefit.

A food-first approach is usually the simplest and safest starting point. If symptoms persist, worsen, or are accompanied by other changes, professional assessment is more appropriate than increasing supplement doses.

Conclusion

Biotin is an essential vitamin that supports energy metabolism, nervous system function, and the maintenance of normal hair, skin and nails. However, deficiency is uncommon in the UK, and evidence for high-dose biotin improving hair or skin in biotin-sufficient people is limited.

For pharmacy customers, the key message is balance: meet biotin needs through diet where possible, be cautious with high-dose supplements, and always mention biotin use before blood tests. When concerns such as hair loss or brittle nails arise, identifying underlying causes is usually more valuable than relying on supplements alone.

Sources

Written by Christian Jakobsson