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Testing Your Patient's Biotin Levels: The Essential Vitamin for Hair, Skin, and Nails

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Testing Your Patient's Biotin Levels: The Essential Vitamin for Hair, Skin, and Nails

Biotin was discovered in 1927; however, it took an additional 40 years before it was recognized as a vitamin. This article will discuss what biotin is, biotin's role in the body, causes of biotin deficiency, and symptoms of deficiency. We’ll then discuss biotin testing and sources of biotin, including dietary and supplements.


What is Biotin (Vitamin B7)?

Biotin is also referred to as vitamin B7. All living things require biotin to function, and some can make biotin on their own, including certain bacteria, yeasts, molds, algae, and certain plants.

Several enzymes are responsible for the digestion of biotin. In the small intestine, biotin will be absorbed into the bloodstream, and the liver will hold and store most biotin.

What is Biotin’s (Vitamin B7’s) Role in The Body?

Biotin acts as a cofactor for five enzymes referred to as carboxylases. These carboxylase enzymes are essential for metabolizing fatty acids, glucose (blood sugar), and amino acids. While these enzymes are found in all cells, carboxylases that are involved in fatty acid metabolism are found in large amounts in the cells of the liver, white adipose (fat) tissue, mammary glands (breast), heart, pancreas, and skeletal muscle. Biotin is required for the proper functions of compounds called histones. Histones are a component of DNA packaging within the cell. Changes to histones can affect the function of DNA, including replication.

What Causes Biotin (Vitamin B7) Deficiency?

Biotin deficiencies are rare, although there are a few scenarios where biotin deficiencies have been seen. Parental nutrition (feeding through intravenous means) without biotin supplementation can lead to deficiency. Infant formulas that do not contain biotin will also cause deficiencies. Lastly, chronic consumption of raw egg whites can lead to biotin deficiency, as a component of raw egg whites, avidin, inhibits biotin absorption in the gastrointestinal tract. Cooking egg whites breaks avidin down and thus does not have the same effect.

There are certain conditions that will increase the risk of a biotin deficiency. Chronic alcohol intake will lower biotin levels. It’s estimated that 15% of those who suffer from chronic alcoholism have a biotin deficiency. Pregnant and lactating women are also more likely to develop a biotin deficiency. For pregnancy, it's estimated that one-third of pregnant women will develop a biotin deficiency, regardless of adequate biotin intake in the diet. For lactating women, biotin levels in the blood and breast milk were lower than expected, even when eating a biotin-rich diet.

Lastly, the genetic disorder biotinidase deficiency can cause low biotin levels. Biotinidase is an enzyme that assists in the amount of circulating biotin in the body. Lack of this enzyme leads to a biotin deficiency even in the presence of normal biotin dietary intake. This disorder can lead to neurological and skin symptoms; if not treated, coma and death can ensue. However, these symptoms and outcomes are preventable if oral biotin is given and continues to be taken throughout life. Because of these outcomes, all infants in the United States, as well as in other countries, are screened for this disorder.

Biotin (Vitamin B7) Deficiency Symptoms

Biotin deficiency symptoms include:

  • Thinning hair that can progress to complete body hair loss
  • Red, scaling rash around orifices of the body, including the mouth, nares, eyes, and perineum
  • Conjunctivitis
  • Ketolactic acidosis (lactic acid production is higher than excretion)
  • Aciduria (high amounts of acid in the urine)
  • Seizures
  • Skin infections
  • Brittle nails
  • Depression
  • Hallucinations
  • Numbness in the arms and legs
  • Lethargy
  • Abnormal distribution of facial fat with rash (known as “biotin deficiency facies”)

Symptoms differ in infants and include lethargy, decreased muscle tone, and developmental delays.

How to Test Biotin (Vitamin B7) Levels

Biotin levels can be measured in the blood and urine. Access Medical Laboratories offers a vitamin B7 test with a reference range of 133–329 picomoles per liter (pmol/L). Biotin is also found on blood micronutrient tests such as the Spectracell Micronutrient test.

Urine measurements of biotin should be between 18–127 nanomoles (nmol) per 24 hours.

How to Get Enough Biotin (B7) from Your Diet

The National Academies of Sciences, Engineering, and Medicine formed a Food and Nutrition Board that created Dietary Reference Intakes (DRI) for vitamins and minerals. The Recommended Dietary Allowance, known as RDA, is a type of DRI. RDA is defined as the average daily amount of a vitamin or mineral required to reach nutritional adequacy in 97-98% of healthy people. In the event that there is not enough evidence to create RDAs for a vitamin or mineral, Adequate Intake (AI) measurements will be formed. AIs are defined as levels assumed to reach nutritional adequacy. AIs were created for biotin.

AIs for Biotin

Pregnant and lactating women often have different DRIs due to their unique nutritional requirements. The AI for biotin of pregnant women aged 14-50 years is 30 mcg. For lactating women aged 14-50 years, the AI of biotin is 35 mcg.

Food Sources of Biotin

Estimates of dietary biotin intake have not been computed in the United States. However, other Western countries estimate dietary biotin intake between 35-70 mcg/day, meaning most people reach an adequate intake of biotin.

Biotin (Vitamin B7) Supplements

Biotin can be found in b-complexes and as a stand-alone supplement. Specific multivitamins may also contain biotin. Supplements often contain the free form of biotin, which has a 100% absorption rate.

It's important to note that there have been no reported adverse health effects when taking high levels of biotin, whether via supplement or intravenously. However, biotin intake may interfere with laboratory processing and thus give false levels of certain markers. Specific labs use a technology that includes biotin; thus, supplemental biotin can interfere with the processing of these labs.

These labs include thyroid hormones and vitamin D (as 25-hydroxyvitamin D). Specific markers for cardiovascular health can also be affected. N-terminal pro-brain natriuretic peptide, a test used to diagnose congestive heart failure, and troponin, a test used to confirm a myocardial infarction or heart attack, can also be affected.

The Food and Drug Administration (FDA) recommends questioning all patients about the use of supplements, especially biotin, and to consider lab errors in tests that do not match the patient's symptomatology.



Biotin is an important b-vitamin essential for life. Biotin's effects are of utmost importance, affecting the way DNA works and the metabolism of the macronutrients fats, carbohydrates, and proteins. Biotin testing can be useful to ensure proper levels. Knowing food sources can help to ensure the prevention of biotin deficiencies and if supplementation is indicated. For providers, it's especially important to ask about biotin supplementation, as it can interfere with critical testing.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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