According to research reviewed by Gram, very high doses of nicotinamide, a form of vitamin B3, can cause severe acute liver injury. A 2026 case report described a 20-year-old woman who developed liver damage after ingesting 15 grams, far above typical supplement doses. She recovered with supportive hospital care.
According to research reviewed by Gram, taking a very high dose of nicotinamide, a form of vitamin B3, may cause sudden and serious liver damage. The report, published in 2026 in ACG Case Reports Journal, describes a 20-year-old woman who took 15 grams of nicotinamide on purpose. Within a short time she had vomiting, stomach pain, and dangerously low blood pressure, and her liver blood tests rose sharply. Doctors checked for viral, immune, metabolic, and blood vessel causes and found none. She improved with supportive hospital care. This is a single case, so it cannot prove how common the problem is. It does show that supplements sold as safe can cause serious harm when taken in very large amounts.
Key Statistics
A 2026 case report published in ACG Case Reports Journal described a 20-year-old woman who developed severe acute liver injury after intentionally ingesting 15 grams of nicotinamide, a form of vitamin B3.
In the 2026 case report, the patient had vomiting, upper stomach pain, and transient low blood pressure before her liver blood tests rose sharply and her blood showed clotting problems.
The 2026 case report found no viral, autoimmune, metabolic, or blood vessel cause for the liver injury, pointing instead to nicotinamide overdose as the likely trigger.
The Quick Take
- What they studied: Can a very large dose of nicotinamide, a form of vitamin B3 sold as a dietary supplement, cause sudden and severe liver damage?
- Who participated: One woman, age 20. She took a very large amount of nicotinamide on purpose and was treated in a hospital. The report describes only her case.
- Key finding: Her liver tests worsened quickly, and she developed blood-clotting problems. Other common causes of liver damage were tested for and ruled out, which points toward the nicotinamide. She recovered with supportive treatment. Because this is one case, the finding is a warning sign, not proof of how often this happens.
- What it means for you: Vitamin B3 is safe in normal amounts, but supplements can be harmful in very large doses. Stay within label directions, avoid stacking multiple supplements that contain B3, and get emergency care right away if you take too much and feel sick.
The Research Details
This is a case report, a detailed write-up of one patient’s illness and treatment. Researchers describe the woman’s symptoms, the timeline of her worsening liver tests, and the results of the tests they ran to look for other causes of liver damage.
The team tested for viral infections, immune system diseases that attack the liver, metabolic disorders, and problems with blood flow to the liver. They also documented how she was treated, including N-acetylcysteine, an antidote often used for liver injury, along with vitamin K and replacement of body salts, called electrolytes.
Because the report follows a single patient closely, it can capture details that large studies often miss, such as the order in which symptoms and lab changes appeared. It cannot show how often the problem happens in the wider population.
Case reports are often the first sign that a risk exists. When a doctor sees a rare or unexpected problem, writing it up helps others recognize it sooner. This case is useful because the patient had no other clear cause for her liver injury, which makes the nicotinamide link easier to consider.
However, a single case cannot establish cause and effect on its own. Larger studies, or reports from poison control centers and hospitals, would be needed to judge how common this injury is and how much of a dose is risky.
The report includes a careful timeline, a broad panel of tests to rule out other causes, and a clear treatment history, which are strengths for a case report. It was published in a peer-reviewed journal.
The main limitation is the sample size of one. The report also relies on the patient’s account of how much she took, and the journal’s impact factor was not available for this summary. Readers should treat it as an important warning rather than a definitive measure of risk.
What the Results Show
The woman arrived at the hospital with vomiting, pain in the upper stomach, and a brief drop in blood pressure. These symptoms appeared after she took 15 grams of nicotinamide. For comparison, typical supplement doses are measured in milligrams, and 15 grams is roughly 15,000 milligrams.
Her liver function tests worsened quickly. The enzymes that signal liver cell damage rose sharply, which is called marked transaminitis. Her blood also showed coagulopathy, meaning it had trouble clotting normally. This is an important sign because the liver makes many clotting proteins, so damage can show up in blood clotting.
She did not develop hepatic encephalopathy, a confusion or drowsiness that can happen when the liver fails to clear toxins from the blood. Her doctors ruled out viral, autoimmune, metabolic, and blood vessel causes, which strengthens the link to the supplement.
She improved with supportive care. Treatments included N-acetylcysteine, vitamin K to help blood clot, and correction of electrolytes. The report does not describe lasting damage, but the case shows that the liver can be seriously affected within a short period.
The authors suggest that nicotinamide overdose may be under-recognized. Many people think supplements are harmless because they are sold without a prescription and labeled as natural. This case challenges that belief by showing that a common nutrient can become toxic at very high doses.
The case also highlights how important it is for clinicians to ask about supplement use. A patient may not mention a supplement unless asked directly, which can delay the right diagnosis.
Vitamin B3 has a long history of safe use, and it is an essential nutrient found naturally in many foods. Niacin, another form of B3, is known to cause side effects at high doses, including skin flushing and, in some cases, liver problems. Those liver effects have been reported mostly with high-dose niacin used to treat cholesterol.
Liver injury from nicotinamide specifically appears to be less commonly reported. This case adds to the picture by describing severe acute injury after a very large intentional dose. It fits with the general principle that high-dose vitamins can carry risks, and it supports the upper intake limits set by health authorities.
The most important limitation is that this is one patient. A single case cannot tell us how often this happens, what dose is dangerous for most people, or whether some people are more vulnerable.
The dose was taken intentionally, in a large amount at once. That situation may differ from long-term use of lower doses. The report also depends on the patient’s account of the amount she took and the timing of her symptoms.
Finally, the report does not show long-term outcomes, so it is unclear whether the liver fully recovered over months or years.
The Bottom Line
Confidence level: moderate that very high doses of nicotinamide can cause serious liver injury, based on this detailed case and the known risks of high-dose B3 forms. Confidence is low about the exact dose that is risky for most people.
Practical steps: Follow the label directions on any supplement. For most adults, the tolerable upper intake level for supplemental niacin forms, including nicotinamide, is 35 mg per day, according to U.S. health authorities. Check labels for B3 in multivitamins, energy products, and skin supplements so you do not stack doses. Talk with a doctor or pharmacist before taking high-dose vitamins, especially if you have liver disease or take other medicines.
If someone takes a large amount of any supplement and develops vomiting, stomach pain, dizziness, yellowing of the skin or eyes, or unusual bleeding or bruising, seek emergency care right away.
Anyone who takes vitamin B3 or nicotinamide supplements, including people taking multivitamins, skin-health products, or high-dose formulas, should care. People with existing liver disease, heavy alcohol use, or those taking medicines that affect the liver should be especially careful and speak with a clinician before using high-dose supplements.
Most people who eat a balanced diet and take standard multivitamins do not need to worry about this specific risk. Clinicians treating people with unexplained liver injury may also find it useful to ask about supplement use.
This report describes a rapid event. In the case, liver tests worsened within a short time after the overdose, and the patient improved with hospital treatment over the following days.
For people who take supplements at normal doses, there is no timeline for harm because normal doses are not expected to cause liver injury. If you have taken too much, symptoms can appear within hours to a day, so get medical help right away rather than waiting. Recovery timelines vary, and the report does not describe long-term follow-up.
Frequently Asked Questions
Can too much vitamin B3 damage the liver?
Very high doses of vitamin B3 in the nicotinamide form may cause severe liver injury. A 2026 case report described a 20-year-old woman who developed acute liver damage after taking 15 grams. Most supplements contain far less, and the adult daily upper limit for supplemental niacin forms is 35 mg.
How much nicotinamide is safe to take per day?
For most adults, the tolerable upper intake level for supplemental niacin forms, including nicotinamide, is 35 mg per day, according to U.S. health authorities. Follow label directions and ask a doctor or pharmacist before taking high-dose products, especially if you have liver disease.
What are the warning signs of liver injury from a supplement overdose?
In a reported case of nicotinamide overdose, early signs included vomiting, upper stomach pain, and brief low blood pressure. Liver blood tests rose quickly, and blood clotting became impaired. Anyone who suspects they took too much and has these symptoms should seek emergency care or call poison control immediately.
Are vitamin B3 supplements generally safe to take?
Vitamin B3 is an essential nutrient, and amounts found in food are generally safe. High-dose supplements carry real risks, as a 2026 case report showed. Sold without a prescription does not mean harmless, so staying within label doses and reviewing all supplements with a clinician reduces risk.
Want to Apply This Research?
- Log every supplement you take, along with the exact amount of vitamin B3 or nicotinamide listed on the label in milligrams. Add up your total daily B3 from all products, including multivitamins. Flag any day when the total goes above 35 mg, and set a reminder to review that day with a clinician if it happens regularly.
- Before adding a new supplement, check the label for B3, niacin, or nicotinamide and compare the amount to your daily total. Avoid taking extra doses to ‘speed up’ results. If you accidentally take more than the label directs, record the time and amount and contact a doctor or poison control right away.
- Review your supplement log every month to catch any new products that add B3 to your routine. Update the log whenever a doctor changes your medicines or supplements. If you have a liver condition or take medicines that affect the liver, ask your clinician whether periodic liver blood tests are appropriate for your situation.
This summary is based on a single case report describing one patient and is provided for general education only. It is not medical advice and cannot establish how common this problem is or what dose is safe for you. Do not change or stop any medicine or supplement without speaking to a qualified healthcare provider. If you think you have taken too much of any supplement and feel unwell, seek emergency medical care or contact your local poison control center right away.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.