Notebook entry

Nutrafol Side Effects, and Who Should Avoid It

Stomach upset in the men's trial, biotin and blood tests, vitamin D stacking, liver-injury reports and medicine interactions: the side-effect record, with a source for every line.

Sources read Sep 22, 2026Not reviewed by a clinician

Nutrafol is usually tolerated, but it is not free of side effects: in its 2025 men's trial, two participants withdrew because of moderate stomach upset that investigators judged probably related, and case reports describe vitamin D levels pushed too high and liver injury. People on blood thinners or other regular medicines, pregnant people and anyone with liver disease should talk to a doctor before starting it.

This entry is information only, written from published sources on 22 September 2026 and not reviewed by a clinician. If you think a supplement is making you unwell, stop and speak to a doctor or pharmacist.

What the trials recorded

The direct answer: the trials mostly describe the capsule as well tolerated, and the men's trial also records stomach upset serious enough for two people to leave.

The 2025 men's trial enrolled 112 men. Of those who did not finish, two left because of moderate gastrointestinal upset judged probably related to the supplement, and one because of an adverse event judged unrelated. The paper also tracked sexual function with a standard questionnaire and found no trend in either group, which is relevant because sexual side effects are a common worry with prescription hair-loss medicines. The 2018 women's trial reported no adverse events, and the 2021 menopause trial described the supplement as well tolerated.

Nutrafol's men's product page, read the same day, says its clinical studies saw no reported side effects. The men's trial paper is the more detailed and more reliable source, and it records the two withdrawals. That gap is one reason our Nutrafol review gives the brand 1 of 2 points for safety candour.

Biotin and blood tests

The direct answer: the biotin in hair supplements can make some laboratory tests read falsely high or falsely low, and the FDA singles out the troponin test used to diagnose heart attacks.

Many blood tests use a chemical pairing that relies on biotin, so extra biotin in the blood can interfere with the result. An FDA page on biotin interference with troponin tests, current as of 21 June 2022, lists troponin assays that remained vulnerable after its 2017 safety communication and warns that falsely low troponin results can lead to a missed diagnosis. The 2025 case report adds that high biotin intake has been linked with falsely suppressed thyroid-stimulating hormone results.

Whatever the amount in your capsule, the practical step is the same: tell whoever orders your blood work that you take a biotin-containing supplement, and let them decide whether to pause it. The full story is in biotin: when it helps, and the lab-test warning.

Stacking vitamins

The direct answer: a multi-ingredient capsule adds to whatever else you take, and a published case shows how that can push a level too high.

The 2025 case report in JAAD Case Reports describes a 72-year-old woman, treated for hair shedding, who was already taking a separate vitamin D supplement and then added Nutrafol, not knowing it contained vitamin D. Her blood level came back at 121.8 ng/mL against a normal range of 30 to 80. It stayed high after she cut back her separate vitamin D, and fell to 86.5 ng/mL, close to normal, only after she also stopped the hair supplement. She had no symptoms, but the authors note that vitamin D toxicity, though rare, can cause dangerous calcium levels. The American Academy of Dermatology separately warns that large amounts of vitamin A or selenium can themselves cause hair loss.

The liver question

The direct answer: several botanicals in Nutrafol appear in liver-injury grading schemes, and at least one case of acute liver injury after Nutrafol use has been published.

The same case report lists six ingredients in the Nutrafol label it examined that carry a likelihood score in the US Drug-Induced Liver Injury Network scheme: turmeric, ashwagandha, horsetail, saw palmetto, kelp minerals and resveratrol, with turmeric the highest graded. It cites a published case of a 26-year-old woman who developed jaundice and raised liver enzymes after taking Nutrafol, whose liver tests improved after she stopped. One case does not measure a risk for everyone, but its authors advise that people with liver disease, or taking other medicines that stress the liver, avoid supplements with these ingredients.

Who should talk to a doctor first

The direct answer: anyone on regular medicines, anyone pregnant, trying to conceive or breastfeeding, anyone with liver disease, and anyone whose hair loss has not been diagnosed.

Blood thinners and other medicines. Nutrafol's own ingredient page asks people with a medical condition or taking medicines, especially anticoagulant and blood-thinning drugs, to consult a physician first.
Pregnancy and breastfeeding. The NIH's complementary-health centre says saw palmetto may be unsafe during pregnancy or while breastfeeding.
Liver disease. See the case report above.
Fish allergy. The men's formula lists marine collagen peptides.
Thyroid tests or heart symptoms. Mention the biotin before any blood test.
Undiagnosed hair loss. A supplement can delay the diagnosis of thyroid disease, iron deficiency or other causes; our entry on getting iron, ferritin and vitamin D tested first explains why that order matters.

How to report a reaction

The direct answer: stop the product, see a doctor, and consider telling the FDA.

The FDA's page on reporting dietary supplement problems, current as of 13 March 2025, sends consumers to its online Safety Reporting Portal, where a private citizen can file a voluntary report. Because supplements are not reviewed before sale, these reports are part of how problems come to light. Keep the product's packaging and label, since the lot number and ingredient list help anyone investigating.

If you want to try it anyway

Keep the label, not the marketing page, and show it to your doctor or pharmacist. Keep a note of when you started, what else you take and any symptoms. If you buy through our link to see Nutrafol's current plans, we may earn a commission on a first order; it does not change anything written here.

Side-effect questions

Does Nutrafol cause weight gain?

We found no report of weight gain in the Nutrafol trials we read, and the men's trial did not list it among reasons people left. If you notice a change in weight after starting any supplement, raise it with a doctor rather than assuming a cause.

Can Nutrafol cause hair shedding at first?

We found no trial that measured an initial shed with Nutrafol, so we cannot say. Shedding has many causes, including stress, illness and stopping other treatments, and a dermatologist can tell you which is likely.

Is Nutrafol safe to take long term?

The published trials ran for six months, with one longer women's study, so long-term safety data is limited. Ingredients such as vitamin D can build up when combined with other supplements, which is a reason to review what you take with a doctor.

Does Nutrafol affect testosterone or sexual function?

The 2025 men's trial tracked sexual function with a standard questionnaire and found no trend in either the supplement or placebo group. It did not report hormone levels in the parts we read.

Should I stop Nutrafol before a blood test?

Ask the person ordering the test. Biotin can distort some results, including troponin and thyroid tests, and they can tell you whether and how long to pause.