Biotin, blood tests, and the number on your bottle

Exhibit 01

What a Daily Value is, and what 1050% of one means

Before the number means anything, the thing it is a percentage of has to be clear. A Daily Value is not a dose, not a target and not a limit. It is a single reference figure per nutrient, fixed so that one percentage can be printed on every package in the country.

NIH puts this label’s figure plainly: “The DV for biotin is 30 mcg for adults and children age 4 years and older.” The panel prints 315 mcg. Divide 315 by 30 and you get 10.5, which is 1050%, and the label has printed exactly that. We checked the other five percentages our sources give a Daily Value for as well, and all six are arithmetically right. That is worth saying before anything else, because the rest of this post is about what a number means rather than whether it is true.

What the percentage does not carry is any judgement. It knows nothing about your age, your diet or your medication. Three figures on this panel are over 100%: vitamin E at 107%, chromium at 217% and biotin at 1050%. Neither chromium nor biotin has an upper limit established; vitamin E’s is 1,000 mg a day and the 16 mg here is far under it. The percentages guide works the general case through.

So 1050% means one thing: this serving carries ten and a half times the figure chosen for the label, not ten and a half times what a body can take. The reason biotin deserves its own post has nothing to do with nutrition.

Exhibit 02

What NIH and FDA actually record about biotin

Biotin is singled out by two federal agencies for a reason that has nothing to do with how much of it a person needs. It gets into the chemistry of certain laboratory tests and changes the answer they give.

The tests at issue are laboratory assays. NIH records falsely altered results for “hormones (such as thyroid hormone) and other analytes such as 25-hydroxyvitamin D”, and specifically “falsely decreased levels of thyroid stimulating hormone (which could lead to a misdiagnosis of thyrotoxicosis) and N-terminal pro-brain natriuretic peptide (which could result in a failure to identify congestive heart failure)”. A thyroid panel is an ordinary test. So is a vitamin D level.

And then the line that puts the rest of this post in proportion: “A patient with a high intake of supplemental biotin died following a troponin test (to help diagnose a heart attack) that gave a falsely low result because the test was subject to biotin interference.”

Read that slowly. The test used to detect a heart attack returned a number lower than the truth, because it was subject to biotin interference, and FDA reports that it has “continued to receive adverse events reports indicating biotin interference caused falsely low troponin results”. A result wrong in the reassuring direction is worse than no result at all.

And now the size of it, before you read another sentence. The amounts in those reports are 10 to 300 milligrams a day, and the single dose that moved a thyroid test was 10 milligrams. Ten milligrams is ten thousand micrograms. This label carries 315 micrograms, which is about a thirty-second of the smallest of them. Everything above is true and none of it describes this bottle. The next exhibit does that arithmetic properly, and this paragraph is here so that nobody reads the one above it on its own.

Exhibit 03

Now the sizes, which is the other half of the same story

Everything above is true and none of it is about 315 micrograms. The amounts in those reports are in a different unit, and a page that showed you the 1050% without this figure would be selling you a fright.

NIH gives the case-report range: “A few recent case reports have described findings falsely indicating Graves' disease and severe hyperthyroidism in patients taking 10-300 mg biotin per day.” And the single-dose finding: “Even a single 10 mg dose of biotin has interfered with thyroid function tests administered within 24 hours.”

Ten milligrams is ten thousand micrograms. This label carries 315 micrograms in a serving of two capsules, the whole daily amount at the printed directions. That is roughly a thirty-second of the smallest interference figure in the sources we opened, and roughly a nine-hundredth of the top of the case-report range.

So this bottle is not a dose those reports describe, and we are not going to imply it is. One more thing belongs here, in the label’s favour: “The FNB was unable to establish ULs for biotin because there is no evidence in humans that biotin is toxic at high intakes.” The interference problem is a measurement problem rather than a poisoning problem.

Exhibit 04

The one thing worth doing, which is free

The actionable part of this subject is one sentence said out loud in a waiting room. It is duller than the 1050%, and it is the only instruction on this page.

NIH records what the federal advice actually is, and it is addressed to the clinician rather than to you: “FDA advises health care providers to ask their patients about any supplements they may be taking that contain biotin and to consider biotin interference as a possible source of error if laboratory test results do not match the clinical presentation of the patient.”

This is a blood sugar support supplement, so the people who buy it are people who have blood drawn. That is the entire reason biotin leads this site. The conversation NIH describes only happens if somebody starts it, and you are the one holding the bottle.

1. Say what you take

   The product name, and that it is a dietary supplement.

2. Say how much biotin

   315 micrograms a serving, which is what the panel prints. The unit matters more than the number: micrograms, not milligrams.

3. Say how often

   The directions read: As a dietary supplement, take two (2) capsules daily with food and an 8 oz. glass of water. So the 315 micrograms is a daily figure at the printed instruction.

Two things not to read into that. It is not a warning to stop taking anything, and this site would have no basis to issue one. It is not a claim that 315 micrograms has ever changed a result, because nothing we read says that.

One closing credit, because it belongs to the label. A panel printing Biotin and a percentage and no weight would leave you nothing to say at the clinic. This one gives you the sentence, and the label page transcribes the rest.