What is biotin?
Biotin, also known as vitamin B7 or vitamin H, is a water-soluble B-complex vitamin that helps the body convert food into energy. It is essential for the health of hair, skin, and nails. Biotin can be found in small amounts in many foods such as eggs, milk, salmon, lentils, seeds, and nuts. It can also be taken as an oral supplement.
Biotin supplements have become increasingly popular in recent years, often taken to promote hair, skin, and nail health. But is there a downside to taking biotin supplements? Let’s take a look at the evidence.
Benefits of biotin
There are some studies showing benefits of biotin supplementation:
- May promote hair growth – A few small studies have found that biotin supplements may help thicken hair and reduce hair loss in those with hair thinning or brittle hair.
- May strengthen nails – Some research indicates biotin supplements can help reduce nail brittleness and splitting.
- May improve symptoms of biotin deficiency – Biotin deficiency is rare but can cause symptoms like hair loss, brittle nails, and skin rash. Taking biotin supplements markedly improves these symptoms in deficient individuals.
However, for those without a biotin deficiency, evidence that biotin meaningfully impacts hair, skin, and nails is weak. Many of the studies are small, low quality, or sponsored by biotin manufacturers. More research is needed to confirm benefits.
Is there a recommended daily amount of biotin?
The recommended daily intake (RDI) for biotin is:
- 30 mcg per day for adults
- 35 mcg per day during pregnancy
- 35 mcg per day while breastfeeding
Most people obtain enough biotin through a regular diet containing things like eggs, nuts, seeds, and whole grains. Biotin deficiency is rare.
Those at greater risk of biotin deficiency include:
- Pregnant women
- Individuals with malabsorption conditions like Crohn’s disease
- Those taking certain medications that disrupt biotin absorption, like some anti-seizure medications
Individuals with a known biotin deficiency may benefit from supplementation under medical supervision. But routine supplementation is not necessary for most healthy adults.
Potential downsides of excessive biotin supplementation
While biotin supplements are generally well tolerated when taken at moderate doses, there are some potential downsides to watch out for:
May interfere with medical lab results
Biotin supplements can cause abnormal results on certain medical lab tests, including tests that measure:
- Thyroid hormones
- Cardiac troponin
- Reproductive hormones like estradiol
High dose biotin supplements may cause falsely high or low results.
If taking biotin supplements, let your healthcare provider know and stop supplementation at least 72 hours before having lab work done. Make sure your provider is aware of your biotin intake when interpreting results.
Risk of allergic reaction
Though rare, allergic reactions to biotin supplements are possible. Symptoms may include:
- Hives or itchy skin
- Swelling of the face, lips, or throat
- Breathing difficulties
Those with a known biotin allergy should avoid supplementation. Seek medical care immediately if an allergic reaction occurs.
Too much biotin is excreted in urine
The body does not store excess biotin. Any amounts consumed above the recommended daily intake are simply filtered out in urine.
While not inherently dangerous, this makes taking mega-doses of biotin rather pointless. Money spent on huge biotin supplements may simply end up flushed down the toilet.
May impact absorption of other B vitamins
There is some concern that high doses of biotin could interfere with absorption of other important B vitamins like B5, B6, B9, and B12.
Deficiencies in these vitamins can lead to anemia and neurological symptoms. Those taking large amounts of biotin should be cognizant of this potential interaction with other B vitamins.
Safe upper limits for biotin intake
To reduce the risk of potential side effects, the following upper limits for biotin intake have been established:
- Adults: maximum of 10,000 mcg (10 mg) per day
- Children: maximum of 5,000 mcg (5 mg) per day
Pregnant or breastfeeding women should not exceed the adult upper limit of 10,000 mcg per day.
These recommendations only apply to supplementation, as it is difficult to overconsume biotin from natural food sources alone.
Signs of a biotin overdose
Consuming biotin in excess of the established tolerable upper limit increases the risk of adverse effects. Potential signs and symptoms of a biotin overdose may include:
- Skin rashes
- Nausea
- Diarrhea
- Hyperglycemia
- Adrenal insufficiency
- Kidney damage
If concerning symptoms are experienced, cease supplementation immediately and see a healthcare professional for evaluation. Blood tests can check biotin levels.
Who should not take biotin supplements?
The following groups should avoid supplementation due to lack of safety data:
- Pregnant women
- Breastfeeding women
- Children and infants
Adults over 18 who wish to take biotin supplements should start at low doses under medical supervision and watch for any side effects. Anyone with a known biotin allergy should avoid supplementation completely.
Safe daily doses for biotin supplementation
For healthy adults over 18 without a known biotin deficiency who wish to take supplements, the following daily doses are generally considered safe:
- Cosmetic doses: 2,500 – 5,000 mcg per day
- General health doses: 100 – 300 mcg per day
Doses up to 10,000 mcg per day are likely safe for most adults, but higher amounts increase the risks of side effects without evidence of added benefits.
Always start at the low end of the dosage range and gradually increase as tolerated. Follow label instructions carefully and discuss supplement use with your healthcare provider.
The bottom line
In summary, biotin is an essential B vitamin that plays an important role in energy metabolism and maintenance of healthy hair, skin, and nails. Moderate amounts can be obtained through foods like eggs, salmon, and almonds.
While biotin deficiency is rare, mild supplementation at doses of 100-300 mcg per day is likely safe for most adults and can correct an existing deficiency.
Higher “megadoses” of biotin supplements show little added benefit for those without deficiency and can potentially interfere with lab test results, impact absorption of other B vitamins, and in rare cases trigger allergic reactions or overdose symptoms.
The body excretes excess biotin in urine, making mega-doses rather pointless. For healthy individuals looking to take biotin, mild doses of 2,500-5,000 mcg per day are likely sufficient and safe in most cases.
As with any supplement, it’s best to check with a healthcare provider before starting to identify any potential medication interactions or concerns. Start low, increase gradually, watch for side effects, and take caution with interpretation of laboratory results.