Biotin and D-Biotin: What's the Difference?

Shopping for supplements can sometimes be confusing, particularly if you're trying to choose a biotin supplement. You may see some bottles labeled "d-biotin" and others that simply say "biotin." Fortunately, it doesn't matter which one you select because they're essentially the same product.

Biotin and d-biotin are basically synonyms for one another, according to the National Center for Biotechnology Information. Biotin is one of the B vitamins, and the "d" indicates that its most natural and active form is in that product. But, if you don't see the "d," that doesn't necessarily mean you're not getting the most common bioactive form of this important vitamin.

"You'll probably get d-biotin regardless of what's on the label," says Robin Foroutan, RDN, an integrative registered dietitian at the Morrison Center in New York City. "There are several forms of biotin, and d-biotin is the one that is the most active and is most often used in supplements."

Biotin is a B vitamin — vitamin B7 — that performs many functions in the body. It's an important co-enzyme that's required to produce cellular energy from the fats, proteins and carbohydrates you eat. It's also involved in cell signaling, which is the process by which your body's cells communicate with each other, according to the National Institute of Health's Office of Dietary Supplements (ODS).

But what makes biotin supplementation appealing to many people is the vitamin's role in maintaining healthy hair and nails.

"Biotin helps synthesize the proteins that turn into our hair and nails," Foroutan explains. "However, taking biotin supplements will help with problems like hair loss and brittle nails only if your biotin levels are depleted," she adds.

Doctors rarely test people's biotin levels, but because biotin supplements are generally considered safe, it's OK to try taking them if your hair or nails are in poor condition, Foroutan says. Biotin is water-soluble, which means that any excess will be excreted in your urine.

Foroutan recommends taking 5 to 10 milligrams (mg), which is 5,000 to 10,000 micrograms (mcg), of biotin a day, noting that some people don't get results because they take less than that.

If supplements don't seem to help, it's best to consult with your doctor to make sure that your hair loss and brittle nails aren't the result of a medical condition, such as a thyroid disorder.

Because biotin is found in many foods — including beef liver, eggs, salmon, pork, sunflower seeds and sweet potatoes — deficiencies are rare. But some people are more prone to low biotin levels than others.

For example, pregnant or breastfeeding people may need more biotin. According to the ODS, at least a third of pregnant people develop marginal biotin deficiency despite normal intakes, and levels of biotin decrease during breastfeeding even when people exceed the daily adequate intake (AI) of the vitamin, which is 35 micrograms (for all other adults, the AI is 30 micrograms).

Those who follow a vegan diet may not get enough biotin because the top sources of the vitamin are animal products. Moderate to heavy alcohol drinkers also run the risk of being low in biotin because alcohol depletes a lot of the B vitamins, Foroutan says.

In addition to thinning hair and brittle nails, signs of a biotin deficiency, according to the ODS, include:

• A red, scaly rash around the eyes, nose, mouth and groin
• Conjunctivitis (pink eye)
• Lactic acidosis (which occurs when lactate production exceeds lactate clearance) and aciduria (abnormal amounts of acid in urine)
• Seizures
• Skin infection
• Neurological issues such as depression and lethargy

If you do decide to take biotin vitamin it's very important to tell your doctor. While they're generally considered to be safe, they can interact with certain medications, such as anticonvulsants.

In addition, the U.S. Food & Drug Administration warns that taking biotin supplements can interfere with certain medical tests, such as cardiovascular diagnostic tests and hormone tests. This can lead to falsely high or falsely low results, depending on the test.