Biotin deficiency is rare in healthy adults eating a varied diet, but several specific conditions can cause it: genetic disorders, heavy alcohol use, certain medications, pregnancy, gut diseases, and prolonged intake of raw egg whites. The recommended daily intake for adults is 30 mcg, a small amount found widely in foods like eggs (cooked), nuts, seeds, and organ meats. When deficiency does develop, it’s almost always because something is blocking absorption or increasing the body’s demand rather than because of diet alone.
Genetic Causes
The most clear-cut cause of biotin deficiency is an inherited condition called biotinidase deficiency, which affects roughly 1 in 60,000 newborns. The BTD gene provides instructions for making biotinidase, an enzyme your body needs to recycle and release biotin from food. Mutations in both copies of this gene (one from each parent) reduce or eliminate the enzyme’s activity.
Severity depends on how much enzyme activity remains. In the profound form, activity drops below 10% of normal. In the partial form, it sits between 10% and 30%. Most newborns in the United States are screened for this condition at birth, and those who test positive can avoid symptoms entirely with daily biotin supplementation for life.
Chronic Alcohol Use
Heavy, long-term drinking is one of the more common real-world causes of biotin deficiency. Alcohol interferes with the body’s main biotin transporter in the gut, a protein called SMVT. Research published in the American Journal of Physiology found that chronic alcohol exposure significantly reduces both the amount of this transporter and its ability to function. The damage happens at a genetic level: alcohol suppresses the genes that tell cells to produce the transporter in the first place.
This isn’t limited to one section of the digestive tract. Chronic alcohol use impairs biotin absorption in both the small and large intestine, making it a double hit. Biotin deficiency of varying degrees has been reported in a substantial number of people with chronic alcoholism, and it often coexists with deficiencies in other B vitamins.
Pregnancy
Pregnancy increases the body’s demand for biotin, and marginal deficiency during pregnancy is more common than previously thought. The recommended intake rises to 30 mcg daily during pregnancy and 35 mcg during breastfeeding. Even women eating a balanced diet can develop subclinical deficiency during the third trimester, likely because the developing fetus requires increasing amounts of biotin for normal growth. This is one reason prenatal vitamins typically include biotin.
Raw Egg Whites
Raw egg whites contain a protein called avidin that binds to biotin with extraordinary strength, making it completely unavailable for your body to use. Each avidin molecule can latch onto up to four biotin molecules, and the bond is one of the strongest found in nature. Cooking denatures avidin, which is why cooked eggs are actually a good source of biotin rather than a threat to it.
You’d need to consume raw egg whites regularly over weeks or months for this to become a problem. The classic cases in medical literature involve people eating large quantities of raw eggs daily, often bodybuilders or people following unusual diets. Occasional raw egg white in a smoothie or cookie dough isn’t going to cause deficiency on its own.
Inflammatory Bowel Disease
Conditions like Crohn’s disease and ulcerative colitis can impair biotin absorption by damaging the intestinal lining where absorption takes place. In patients with ulcerative colitis specifically, researchers have found a significant decrease in the SMVT transporter, the same protein that alcohol suppresses. With less of this transporter available, less biotin makes it from the gut into the bloodstream.
There is a practical workaround: at higher doses, biotin can be absorbed through passive diffusion, essentially bypassing the damaged transporter system. This means supplementation at pharmacological doses can sometimes compensate for the absorption problem, though the underlying gut inflammation still needs treatment.
Surgical removal of large portions of the intestine creates similar risks. Patients who’ve had extensive gut resection lose physical absorptive surface area, and if they’re also receiving nutrition intravenously without biotin supplementation, deficiency can develop. In documented cases, patients on long-term intravenous feeding who received no biotin orally or intravenously developed severe hair loss that reversed once biotin was added back.
Anticonvulsant Medications
Certain seizure medications lower biotin levels over time. Carbamazepine is the best-studied example. In both human patients and animal studies, long-term carbamazepine use reduces biotin in the blood and liver, and it also decreases the activity of biotin-dependent enzymes in the brain and liver. One measurable consequence is elevated lactate levels in the brain and blood, a sign that energy metabolism is being disrupted.
Phenytoin and other older anticonvulsants have also been linked to lower biotin status, though the mechanisms are less well characterized. If you take seizure medication long-term, your doctor may monitor for signs of B-vitamin depletion or recommend supplementation.
How Deficiency Shows Up
Biotin deficiency tends to develop gradually, and early symptoms are easy to dismiss. The most recognizable signs include thinning hair or hair loss, a red scaly rash around the eyes, nose, and mouth, and brittle nails. As deficiency worsens, neurological symptoms can appear: numbness and tingling in the hands and feet, depression, fatigue, and in severe cases, hallucinations or seizures.
In infants with biotinidase deficiency, symptoms can be more dramatic and appear within the first few months of life, including low muscle tone, breathing problems, and developmental delays. Early detection through newborn screening and immediate supplementation prevents these outcomes entirely.
How Deficiency Is Detected
Diagnosing biotin deficiency isn’t as straightforward as a single blood test. In healthy people, serum biotin typically ranges from 133 to 329 pmol/L, and urinary biotin excretion falls between 18 and 127 nmol over 24 hours. Values below these ranges suggest deficiency, but serum biotin alone isn’t always reliable because levels can fluctuate.
A more sensitive marker is urinary 3-hydroxyisovaleric acid. When biotin is low, one of the enzymes that depends on it can’t do its job, and a byproduct called 3-hydroxyisovaleric acid accumulates and spills into the urine. Elevated levels of this compound can catch deficiency earlier than a drop in blood biotin levels. In practice, doctors often use a combination of clinical symptoms, blood levels, and urine markers to confirm the diagnosis.
Who Is Most at Risk
Putting it all together, the people most likely to develop biotin deficiency fall into a few identifiable groups:
- People with biotinidase deficiency, whether diagnosed in infancy or, rarely, identified later in life
- Chronic heavy drinkers, due to suppressed absorption across the entire gut
- Pregnant or breastfeeding women, especially those not taking a prenatal vitamin
- People with inflammatory bowel disease or those who’ve had significant intestinal surgery
- Long-term users of certain seizure medications, particularly carbamazepine
- Patients on long-term intravenous nutrition without adequate vitamin supplementation
For most people eating a reasonably varied diet, biotin deficiency is unlikely. The vitamin is produced in small amounts by gut bacteria and is present in a wide range of foods. Deficiency almost always requires a second factor, something blocking absorption, increasing demand, or eliminating dietary intake altogether.