Niacinamide
Pronunciation: nye-ASS-in-a-mide.
- Generic name
- nicotinamide (niacinamide)
- Drug class
- Water-soluble vitamin B3 (B-complex vitamin)
- Form
- Oral dietary-supplement formulations; specific formulations were not established in the reviewed sources
- Route
- Oral dietary supplement; niacinamide is also used in topical skincare products, but topical safety data were not established in the reviewed sources
- Legal status
- Available without a prescription as an oral dietary supplement; regulatory status by country was not reviewed
Availability and supply rules vary by country
Trade names by country: Canada
Australia: · Full directory
What nicotinamide (niacinamide) is and how it works
Niacinamide, also called nicotinamide, is a form of vitamin B3. It occurs naturally in food and is available as an oral dietary supplement. High-dose nicotinamide has been associated in reviewed studies with gastrointestinal symptoms, headache, dizziness, possible effects on insulin sensitivity, low platelet count, reduced serum phosphorus, and liver injury. (1) (2) (3)
Side-effect evidence in the reviewed literature is mainly relevant to high oral doses and does not establish topical skincare safety. Niacinamide should not be confused with nicotinic acid (niacin): flushing is documented for nicotinic acid and was not indicated as a nicotinamide adverse effect in the reviewed sources.
Mechanism of action: how nicotinamide (niacinamide) works
Niacinamide/nicotinamide is a form of the water-soluble B-complex vitamin B3. It is distinct from nicotinic acid/niacin, which is associated with GPR109A-mediated prostaglandin release and flushing. (1) (2) (3)
What nicotinamide (niacinamide) is used for
Vitamin B3 source
Niacinamide is a form of vitamin B3, a water-soluble B-complex vitamin naturally found in foods including bran, yeast, eggs, peanuts, poultry, red meat, fish, whole-grain cereals, legumes, and seeds. (1)
Pellagra treatment context
The reviewed StatPearls source describes nicotinamide for pellagra treatment, including an adult regimen of 100 mg orally every 6 hours and a World Health Organization recommended daily dose of 300 mg in that treatment context. This is not a self-treatment dose recommendation; diagnosis and treatment decisions require a clinician. (1)
Before taking nicotinamide (niacinamide)
Do not take / not appropriate for
- Specific contraindications for niacinamide/nicotinamide were not established in the sources reviewed for this draft. (unresolved evidence gap) (1) (3)
Tell your clinician about
- Diabetes or concerns about blood-glucose control, because decreased insulin sensitivity was reported at 2 grams daily for 2 weeks in studies reviewed.
- Any plan to use a high-dose niacinamide supplement or a product whose vitamin B3 form is unclear.
- Pregnancy, plans for pregnancy, or breastfeeding, because pregnancy- and lactation-specific niacinamide safety and dosing data were not established in the reviewed sources.
- All medicines and supplements being used. A specific nicotinamide drug-interaction list was not established in the reviewed sources.
How to take nicotinamide (niacinamide)
- This side-effects page does not provide a general supplement dose or a personalised treatment plan.
- For pellagra treatment, the reviewed source describes clinician-directed nicotinamide dosing; use of a high-dose supplement should be discussed with a clinician.
- Check whether a product contains niacinamide/nicotinamide or nicotinic acid/niacin, as the adverse-effect profiles discussed in the reviewed sources differ, particularly for flushing.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3)
Missed dose
Missed-dose instructions for niacinamide/nicotinamide were not established in the reviewed sources. Ask the prescriber or pharmacist for advice rather than taking an extra dose.
Overdose
If a large amount of niacinamide/nicotinamide may have been taken, contact a poison-information service or seek urgent medical advice. Prompt medical assessment is particularly important if jaundice, itching, fatigue, nausea, vomiting, severe abdominal symptoms, dizziness, or other concerning symptoms occur. The reviewed sources describe severe liver injury with high vitamin B3 exposures, but the toxicity source does not separately distinguish nicotinamide from nicotinic acid in its management discussion. (2) (3)
Side effects
Evidence reviewed suggests that 500 to 1,000 mg daily used long term appeared well tolerated in the literature review, while adverse effects have been reported at higher doses. The severity, dose relationship, and certainty of individual effects vary between studies. Flushing is not indicated as a nicotinamide adverse effect in the reviewed sources; it is associated with nicotinic acid (niacin).
Nausea and other upper abdominal symptoms
What to notice: Nausea has been reported with high-dose nicotinamide. Vomiting and epigastric pain are also documented in vitamin B3 toxicity literature, although that source does not separately distinguish nicotinamide from nicotinic acid.
What to do: Discuss persistent, severe, or troublesome symptoms with a clinician or pharmacist, particularly if using a high-dose product. (2) (3)
Headache or dizziness
What to notice: Frontal dull headaches, headache, and dizziness have been reported in reviewed studies, in some cases acutely at doses ranging from 1 to 18 grams.
What to do: Discuss persistent, severe, or troublesome symptoms with a clinician, especially after high-dose exposure. (3)
No flushing signal established for niacinamide
What to notice: Flushing is classically associated with nicotinic acid/niacin, not nicotinamide/niacinamide. The reviewed nicotinamide safety review did not indicate flushing as a nicotinamide adverse effect.
What to do: Check the product ingredient and discuss unexpected symptoms with a clinician or pharmacist if the vitamin B3 form is unclear. (1) (3)
Possible blood-glucose or insulin-sensitivity effect
What to notice: Changes in blood-glucose control may be a concern for people with diabetes. Decreased insulin sensitivity was reported at 2 grams daily for 2 weeks in studies reviewed.
What to do: People with diabetes should monitor levels as directed by their clinician and discuss niacinamide supplementation with that clinician. (3)
Possible platelet or phosphorus changes
What to notice: Thrombocytopenia and decreased serum phosphorus were reported at doses of 0.52 to 2 grams daily in studies reviewed.
What to do: Contact a clinician promptly for assessment if there are concerning symptoms or if blood-test changes are identified during high-dose use. (3)
Serious warnings
Possible liver injury with high-dose nicotinamide — urgent
Symptoms: Jaundice, itching, fatigue, nausea, or vomiting may occur with hepatocellular liver injury. Reviewed nicotinamide studies reported parenchymal-cell injury, portal fibrosis, cholestasis, and liver injury at 3 to 9 grams daily for 10 days.
Action: Seek urgent medical assessment for these symptoms. A clinician should assess the product, dose, timing, liver tests, and whether treatment should be continued or stopped. (2) (3)
Severe vitamin B3 toxicity or acute liver failure — emergency
Symptoms: Severe illness with jaundice, marked fatigue, nausea, vomiting, or other signs of serious liver illness after a high-dose vitamin B3 exposure.
Action: Seek emergency medical care immediately. Severe vitamin B3-associated hepatotoxicity has been reported to range to acute liver failure, although the reviewed toxicity source does not separately attribute this management discussion to nicotinamide rather than nicotinic acid. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Drug and supplement interactions | A specific drug-drug interaction list for niacinamide/nicotinamide was not established in the reviewed sources. | Give a clinician or pharmacist a complete list of medicines and supplements before using a high-dose niacinamide product. (3) |
| Diabetes and blood-glucose monitoring | Decreased insulin sensitivity and increased oxidative stress were reported at 2 grams daily for 2 weeks in studies reviewed. | People with diabetes should discuss niacinamide supplementation and blood-glucose monitoring with their clinician. (3) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy and breastfeeding
Pregnancy- and lactation-specific niacinamide/nicotinamide safety and dosing data were not established in the sources reviewed for this draft. Discuss any supplement use with a clinician. (3)
People with diabetes
Decreased insulin sensitivity was reported at 2 grams daily for 2 weeks in studies reviewed. Discuss high-dose supplementation and monitoring with a clinician. (3)
Topical skincare users
Niacinamide is used in topical skincare products, but topical-specific safety data were not established from an authoritative source in this research pass. This page should not be used to infer topical safety. (3)
Monitoring
Before starting
- Confirm whether the product contains niacinamide/nicotinamide or nicotinic acid/niacin.
- For planned high-dose use, discuss the intended dose, duration, existing health conditions, and all medicines and supplements with a clinician.
- People with diabetes should discuss blood-glucose monitoring with their clinician because decreased insulin sensitivity was reported in reviewed high-dose studies.
During treatment
- Monitor for nausea, headache, dizziness, vomiting, abdominal symptoms, jaundice, itching, or fatigue and seek medical advice for concerning symptoms.
- A clinician may assess liver effects, platelet count, serum phosphorus, and blood-glucose control when clinically appropriate for high-dose use; the reviewed sources report these as potential areas of concern but do not establish a universal monitoring protocol.
- Long-term epigenetic effects of chronic high-dose nicotinamide remain an open research question rather than an established adverse effect.
Storage
Storage requirements for oral niacinamide/nicotinamide supplement products were not established in the reviewed sources. Use the exact product packaging and pharmacist advice.
Professional information
Clinician-facing context only. This draft is based on the listed reviewed sources and does not replace current local product information, assessment, or clinical judgement.
All regions
Indication: Niacinamide/nicotinamide oral use
Dose summary: No general supplement dose, country-specific regulatory guidance, RDA, or tolerable upper intake level is provided because these were not established from a directly retrieved authoritative source in this research pass. For pellagra treatment, one reviewed source states 100 mg orally every 6 hours for adults and notes a World Health Organization recommended daily dose of 300 mg in that treatment context.
Renal context: Renal-impairment dosing information was not established in the reviewed sources. (1)
Hepatic guidance
High-dose nicotinamide studies reviewed reported parenchymal-cell injury, portal fibrosis, cholestasis, and liver injury at 3 to 9 grams daily for 10 days. Some older human liver-toxicity reports may have involved nicotinic-acid contamination rather than being solely attributable to nicotinamide.
Overdose note
The reviewed toxicity source describes serious vitamin B3 hepatotoxicity ranging from liver-enzyme elevation to acute liver failure, generally around 3 grams daily and more commonly with sustained-release formulations, but it does not separately distinguish nicotinamide from nicotinic acid in its toxicity-management discussion. High-dose exposure requires clinical product and dose reconstruction. (1) (2) (3)
Frequently asked questions
Does niacinamide cause flushing?
The reviewed sources do not indicate flushing as a niacinamide/nicotinamide adverse effect. Flushing is classically associated with nicotinic acid, also called niacin, which is a different form of vitamin B3. (1) (3)
Can high-dose niacinamide affect the liver?
Yes. Liver injury, including parenchymal-cell injury, portal fibrosis, and cholestasis, was reported in reviewed studies at 3 to 9 grams daily for 10 days. Some older reports may have involved nicotinic-acid contamination. Seek urgent medical assessment for jaundice, itching, fatigue, nausea, or vomiting. (2) (3)
Is niacinamide safe for people with diabetes?
The reviewed studies reported decreased insulin sensitivity at 2 grams daily for 2 weeks. People with diabetes should discuss niacinamide supplementation and blood-glucose monitoring with their clinician. (3)
References
- Vitamin B3StatPearls Publishing, National Center for Biotechnology Information · United States · accessed 2026-08-05 · source 1
- Niacin ToxicityStatPearls Publishing, National Center for Biotechnology Information · United States · accessed 2026-08-05 · source 2
- Possible Adverse Effects of High-Dose Nicotinamide: Mechanisms and Safety AssessmentNational Center for Biotechnology Information · United States · accessed 2026-08-05 · source 3
Brand names by country
Single-ingredient nicotinamide (niacinamide) names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
Canada
- NIACINAMIDE INJ