Drug & supplement interaction

Niacinamide + Metformin

Metformin brand names: Glucophage, Metformin.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Niacinamide and Metformin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Niacinamide and Metformin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Metformin and Niacinamide in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Niacinamide safety at a glance

Niacinamide overall Use caution Usually well tolerated at recommended amounts, but high doses can cause side effects and should be supervised.
Pregnancy Likely Safe When used orally in amounts that do not exceed the tolerable upper intake level (UL) for niacinamide. The UL of niacinamide during pregnancy and lactation is 30... Read the full pregnancy detail
Breastfeeding Likely Safe When used orally in amounts that do not exceed the tolerable upper intake level (UL) for niacinamide. The UL of niacinamide during pregnancy and lactation is 30... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Metformin and Niacinamide? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metformin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metformin is filed under 5 classifications — including organic cation transporter 2 (oct2) substrates, antidiabetes drugs, oral drugs. Niacinamide has documented interactions with 4 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), carbamazepine (tegretol) (moderate) and primidone (mysoline) (moderate) — and none of Metformin’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Niacinamide Does Interact With Other Medications

Niacinamide has 124 moderate known drug interactions in our database — Metformin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 124 No known interaction 2,706 (incl. Metformin)
Taking anything else?

Check Another of Your Medications Against Niacinamide

Covers the 2,830 medications we’ve checked against Niacinamide. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Niacinamide and Metformin May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas / Diarrhea / Vomiting / Nausea Additional detail

    Niacinamide

    “Orally, large doses of niacinamide can cause gastrointestinal disturbances including nausea, vomiting, heartburn, anorexia, epigastric pain, flatulence, and diarrhea.”

    Niacinamide · Natural Medicines adverse-effect record, reported in anorexia.

    6 sources cited
    1. 6243. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000). Washington, DC: National Academy Press, 2000. Available at: http://b
    2. 11694. Anon. Niacinamide Monograph. Alt Med Rev 2002;7:525-9.
    3. 11695. Miralbell R, Mornex F, Greiner R, et al. Accelerated radiotherapy, carbogen, and nicotinamide in glioblastoma multiforme: report of European Organization for Research and Treatment of Cancer trial 22933. J Clin Oncol 1999;17:3143-9. PubMed
    4. 11696. Fatigante L, Ducci F, Cartei F, et al. Carbogen and nicotinamide combined with unconventional radiotherapy in glioblastoma multiforme: a new modality treatment. Int J Radiat Oncol Biol Phys 1997;37:499-504. PubMed
    5. 11697. Hoskin PJ, Stratford MR, Saunders MI, et al. Administration of nicotinamide during chart: pharmacokinetics, dose escalation, and clinical toxicity. Int J Radiat Oncol Biol Phys 1995;32:1111-9. PubMed
    6. 107709. Ketteler M, Wiecek A, Rosenkranz AR, et al. Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial. Kidney Int Rep 2020;6(3): PubMed

    Metformin

    Listed in the ADVERSE REACTIONS section of the FDA label for Metformin. Read the label on DailyMed ›

  • Stomach upset Additional detail

    Niacinamide

    “Orally, niacinamide is well tolerated in amounts typically found in food. When used topically and orally in higher doses, niacinamide seems to be generally well tolerated.

    Most Common Adverse Effects:

    Orally: Dizziness, drowsiness, itching, gastrointestinal disturbances, headache, and rash.

    Topically: Burning sensation, itching, and mild dermatitis.”

    Niacinamide · Natural Medicines adverse-effect record, reported in cluster headache.

    Metformin

    Listed in the ADVERSE REACTIONS section of the FDA label for Metformin. Read the label on DailyMed ›

  • Dizziness / Headache Additional detail

    Niacinamide

    “Orally, large doses of niacinamide can cause dizziness, drowsiness, and headaches.”

    Niacinamide · Natural Medicines adverse-effect record, reported in vertigo.

    5 sources cited
    1. 11694. Anon. Niacinamide Monograph. Alt Med Rev 2002;7:525-9.
    2. 11695. Miralbell R, Mornex F, Greiner R, et al. Accelerated radiotherapy, carbogen, and nicotinamide in glioblastoma multiforme: report of European Organization for Research and Treatment of Cancer trial 22933. J Clin Oncol 1999;17:3143-9. PubMed
    3. 11696. Fatigante L, Ducci F, Cartei F, et al. Carbogen and nicotinamide combined with unconventional radiotherapy in glioblastoma multiforme: a new modality treatment. Int J Radiat Oncol Biol Phys 1997;37:499-504. PubMed
    4. 11697. Hoskin PJ, Stratford MR, Saunders MI, et al. Administration of nicotinamide during chart: pharmacokinetics, dose escalation, and clinical toxicity. Int J Radiat Oncol Biol Phys 1995;32:1111-9. PubMed
    5. 107709. Ketteler M, Wiecek A, Rosenkranz AR, et al. Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial. Kidney Int Rep 2020;6(3): PubMed

    Metformin

    Listed in the ADVERSE REACTIONS section of the FDA label for Metformin. Read the label on DailyMed ›

  • A skin rash Additional detail

    Niacinamide

    “Orally, large doses of niacinamide are associated with occasional reports of rashes, itching, and acanthosis nigricans, though a meta-analysis of 19 clinical studies suggests that dermatological adverse event rates are similar between niacinamide and control. Topically, application of niacinamide in a cream has been reported to cause a burning sensation, itching and pruritus, crusting, and mild dermatitis.”

    Niacinamide · Natural Medicines adverse-effect record, reported in dermatitis.

    6 sources cited
    1. 4880. Pozzilli P, Browne PD, Kolb H. Meta-analysis of nicotinamide treatment in patients with recent-onset IDDM. The Nicotinamide Trialists. Diabetes Care 1996;19:1357-63. PubMed
    2. 11695. Miralbell R, Mornex F, Greiner R, et al. Accelerated radiotherapy, carbogen, and nicotinamide in glioblastoma multiforme: report of European Organization for Research and Treatment of Cancer trial 22933. J Clin Oncol 1999;17:3143-9. PubMed
    3. 11697. Hoskin PJ, Stratford MR, Saunders MI, et al. Administration of nicotinamide during chart: pharmacokinetics, dose escalation, and clinical toxicity. Int J Radiat Oncol Biol Phys 1995;32:1111-9. PubMed
    4. 14504. Papa CM. Niacinamide and acanthosis nigricans (letter). Arch Dermatol 1984;120:1281. DOI
    5. 107709. Ketteler M, Wiecek A, Rosenkranz AR, et al. Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial. Kidney Int Rep 2020;6(3): PubMed
    6. 116766. Oh HJ, Bae SC, Oh IJ, et al. Nicotinamide in Combination with EGFR-TKIs for the Treatment of Stage IV Lung Adenocarcinoma with EGFR Mutations: A Randomized Double-Blind (Phase IIb) Trial. Clin Cancer Res 2024;30(8):1478-1487. PubMed

    Metformin

    Listed in the ADVERSE REACTIONS section of the FDA label for Metformin. Read the label on DailyMed ›

Reported for Niacinamide but not commonly for Metformin: a low platelet count, drowsiness, heartburn and reduced appetite.

Effects for Metformin come from the ADVERSE REACTIONS section of its FDA label; effects for Niacinamide come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Niacinamide in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Safe

When used orally in amounts that do not exceed the tolerable upper intake level (UL) for niacinamide. The UL of niacinamide during pregnancy and lactation is 30 mg daily for those 14-18 years of age and 35 mg daily for those 19 years and older. There is insufficient reliable information available about the safety of larger oral doses of niacinamide or topical niacinamide; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Metformin Is Prescribed For, and What Niacinamide Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Metformin is a prescription medicine with approved uses on its FDA label. Niacinamide is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Metformin is prescribed for: Metformin is used to improve blood sugar (glucose) control in people with type 2 diabetes mellitus. It is always used together with diet and exercise, not instead of them. Metformin hydrochloride tablets and oral solution are approved for adults and children 10 years and older. Metformin hydrochloride extended-release tablets — including brands such as Fortamet, Glumetza, and Metformin Hydrochloride Extended Release — are approved for adults only.

Niacinamide has been studied for:

  • Diabetes Natural Medicines rates the evidence for Niacinamide: Possibly Effective Read what the research shows

    Niacinamide for diabetes

    Oral niacinamide does not seem to prevent the onset of type 1 diabetes, although it might slow its progression.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Metformin on your own; if you are taking Niacinamide for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Niacinamide or Metformin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Niacinamide or Metformin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Metformin

This page covers Niacinamide only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin page lists 258 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 217 moderate · 39 minor.

From our pharmacist’s overview on the Metformin page

“Siberian cocklebur is the ingredient I most want anyone taking metformin (Glucophage) to know about. It has caused severe low blood sugar in people, documented in humans, and it should not be combined with any glucose-lowering medication.”

Reviewed by 2 · Jul 18, 2026

Open the Metformin interaction page

One more smart check

Taking Niacinamide as Part of a Dietary Supplement Product? Check It for Interactions

We hold 552 real supplement products containing Niacinamide, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Niacinamide. Even though Niacinamide itself has no known interaction with Metformin, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Niacinamide and Metformin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Niacinamide
Top 25%

#301 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metformin
Top 1%

#29 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Niacinamide reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Niacinamide and Metformin records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Niacinamide

What is Niacinamide?

  • Acne and skin health
  • Pellagra (niacin deficiency)
  • Anti-aging and skin tone
  • Rosacea
  • Protecting against certain skin cancers

Niacinamide (also called nicotinamide) is a form of vitamin B3 used in supplements and skin-care products. It is well established for preventing and treating vitamin B3 deficiency, and there is moderate evidence for some skin uses, but many popular claims are still being studied. It is generally well tolerated at usual doses, but high amounts should be discussed with your doctor or pharmacist.

Not applicable (a form of vitamin B3) · Tablets, capsules, powders, topical creams and serums

An interaction check asks whether these two react with each other — it does not ask whether Niacinamide is a good idea for someone in your situation. Here is what our Niacinamide record says about it on its own.

Niacinamide: dosing

There is no single standardized supplement dose that fits everyone, and the right amount depends on why it is being used and your age and health. For preventing deficiency, intake is usually covered by a normal diet or a standard multivitamin.Skin products and oral supplements vary widely in strength. Do not assume more is better.

From our Niacinamide monograph — the full record covers uses, side effects and every documented interaction.

Read the full Niacinamide monograph & all interactions
Medication

About Metformin

What Is Metformin Used For?

Brand names: Glucophage, Metformin

Metformin is used to improve blood sugar (glucose) control in people with type 2 diabetes mellitus. It is always used together with diet and exercise, not instead of them.

Metformin hydrochloride tablets and oral solution are approved for adults and children 10 years and older. Metformin hydrochloride extended-release tablets — including brands such as Fortamet, Glumetza, and Metformin Hydrochloride Extended Release — are approved for adults only.

See full Metformin drug information
Keep checking

Other Drugs & Niacinamide

Browse every other medication we’ve checked against Niacinamide — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
124Moderate
0Minor
2,705No known interaction
124 Moderate 2,705 No interaction
Moderate

124 interactions

Showing 60 of 124 moderate interactions — see all 124 on the Niacinamide page.

No interaction 2,705 drugs checked — show the list

We also checked Niacinamide against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,705 medications checked with no known interaction — see the full Niacinamide list.

See the full Niacinamide interactions page
See every supplement checked against Metformin, ranked by severity
Evidence & sources

Niacinamide References

The 22 references that drive our Niacinamide monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Pozzilli P, Browne PD, Kolb H. Meta-analysis of nicotinamide treatment in patients with recent-onset IDDM. The Nicotinamide Trialists. Diabetes Care 1996;19:1357-63. PubMed
  2. Greenbaum CJ, Kahn SE, Palmer JP. Nicotinamide's effects on glucose metabolism in subjects at risk for IDDM. Diabetes 1996;45:1631-4. DOI
  3. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000). Washington, DC: National Academy Press, 2000. Available at: http://b
  4. Anon. Niacinamide Monograph. Alt Med Rev 2002;7:525-9.
  5. Miralbell R, Mornex F, Greiner R, et al. Accelerated radiotherapy, carbogen, and nicotinamide in glioblastoma multiforme: report of European Organization for Research and Treatment of Cancer trial 22933. J Clin Oncol 1999;17:3143-9. PubMed
  6. Fatigante L, Ducci F, Cartei F, et al. Carbogen and nicotinamide combined with unconventional radiotherapy in glioblastoma multiforme: a new modality treatment. Int J Radiat Oncol Biol Phys 1997;37:499-504. PubMed
  7. Hoskin PJ, Stratford MR, Saunders MI, et al. Administration of nicotinamide during chart: pharmacokinetics, dose escalation, and clinical toxicity. Int J Radiat Oncol Biol Phys 1995;32:1111-9. PubMed
  8. Papa CM. Niacinamide and acanthosis nigricans (letter). Arch Dermatol 1984;120:1281. DOI
  9. Bourgeois BF, Dodson WE, Ferrendelli JA. Interactions between primidone, carbamazepine, and nicotinamide. Neurology 1982;32:1122-6.
  10. Visalli N, Cavallo MG, Signore A, et al. A multi-centre randomized trial of two different doses of nicotinamide in patients with recent-onset type 1 diabetes (the IMDIAB VI). Diabetes Metab Res Rev 1999;15:181-5. DOI
  11. Rottembourg JB, Launay-Vacher V, Massard J. Thrombocytopenia induced by nicotinamide in hemodialysis patients. Kidney Int. 2005;68(6):2911-2. PubMed
  12. Fabbrocini G, Cantelli M, Monfrecola G. Topical nicotinamide for seborrheic dermatitis: an open randomized study. J Dermatolog Treat. 2014 Jun;25(3):241-5. PubMed
  13. Khodaeiani E, Fouladi RF, Amirnia M, Saeidi M, Karimi ER. Topical 4% nicotinamide vs. 1% clindamycin in moderate inflammatory acne vulgaris. Int J Dermatol. 2013 Aug;52(8):999-1004. PubMed
  14. Zhang Y, Ma T, Zhang P. Efficacy and safety of nicotinamide on phosphorus metabolism in hemodialysis patients: A systematic review and meta-analysis. Medicine (Baltimore). 2018;97(41):e12731. PubMed
  15. Ketteler M, Wiecek A, Rosenkranz AR, et al. Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial. Kidney Int Rep 2020;6(3): PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Niacinamide and Metformin Together: Common Questions

Is it safe to take Niacinamide with Metformin?
We do not list a known interaction between Niacinamide and Metformin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Niacinamide and Metformin have any of the same side effects?
Yes — our sources link each of them separately to 8 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Niacinamide and Metformin used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Niacinamide in each. That is a conversation for your prescriber, especially if Metformin is being adjusted to a target.
How was the Niacinamide and Metformin combination checked?
Interactions in our licensed database are recorded against drug classes. Metformin is filed under 5 classifications, and Niacinamide has documented interactions with 4 drug classes — none of Metformin's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Niacinamide interact with any other medications?
Yes. Niacinamide has 124 documented drug interactions in our database — Metformin is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Metformin interact with any supplements?
Yes. Metformin has documented interactions with 258 supplements in our database — Niacinamide is not one of them. The Metformin interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Niacinamide monograph Uses, safety profile, and every drug interaction in one place Metformin drug information The full plain-English guide to this medication Metformin supplement interactions Every supplement checked against Metformin, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 22 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metformin and Niacinamide?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.