Drug & supplement interaction

Niacinamide + Carbidopa

Carbidopa brand name: Lodosyn.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Niacinamide and Carbidopa 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 Carbidopa

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 Carbidopa 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 Carbidopa and Niacinamide? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Carbidopa

Interactions in our licensed database are recorded against drug classes, not just single drug names. Carbidopa is filed under 3 classifications — including 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 Carbidopa’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 — Carbidopa 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. Carbidopa)
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 Carbidopa 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. One of them is worth acting on rather than waiting out — marked below.

  • A low platelet count Worth acting on Additional detail

    Niacinamide

    “Orally, niacinamide supplementation might increase the risk for thrombocytopenia in patients undergoing hemodialysis. A meta-analysis of small clinical studies shows that taking niacinamide during hemodialysis to reduce phosphate levels is associated with a 2.8-fold increased risk for thrombocytopenia when compared with placebo.”

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

    2 sources cited
    1. 98940. 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
    2. 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

    Carbidopa

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

  • Heartburn / Bloating or gas / Reduced appetite / Diarrhea 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

    Carbidopa

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

  • Drowsiness / Dizziness reported in 5.4% of FDA reports for Carbidopa 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

    Carbidopa

    Listed in the ADVERSE REACTIONS section of the FDA label for Carbidopa, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Stomach upset Additional detail

    Niacinamide

    Recorded for Niacinamide in the same Natural Medicines adverse-effect record shown under Drowsiness / Dizziness above.

    Carbidopa

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

  • Itching / 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

    Carbidopa

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

Showing the 10 most notable of 13 shared effects — ranked by how unusual each one is, not just whether both lists mention it.

Effects for Carbidopa come from the ADVERSE REACTIONS section of its FDA label; effects for Niacinamide come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 52,609 voluntary FDA FAERS reports for Carbidopa that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. 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

Everything else you take

See Every Supplement That Interacts With Carbidopa

This page covers Niacinamide only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Carbidopa page lists 21 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Magnesium (major), 5-htp (moderate), Coffee Charcoal (moderate) and European Mandrake (moderate).

By severity: 2 major · 10 moderate · 9 minor.

From our pharmacist’s overview on the Carbidopa page

“Carbidopa (Lodosyn) keeps levodopa working in Parkinson's disease, so anything that blocks its absorption can cost real motor control, and two of the 21 supplements on this list do exactly that at a level rated major. Magnesium is the one that surprises people: in a human study it cut carbidopa absorption by 81 percent and levodopa's b…”

Reviewed by 2 · Jul 18, 2026

Open the Carbidopa 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 Carbidopa, 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 Carbidopa 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%

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

29 days ago today
Medication Carbidopa
Top 25%

#682 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 20, 2026. The Niacinamide and Carbidopa 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 Carbidopa

What Is Carbidopa Used For?

Brand name: Lodosyn

Carbidopa tablets — sold under the brand name Lodosyn and as generic carbidopa — are used together with levodopa or carbidopa-levodopa to manage symptoms of Parkinson's disease, postencephalitic parkinsonism, and symptomatic parkinsonism that can result from carbon monoxide or manganese poisoning. Carbidopa is never used alone; it always works as a partner to levodopa-based therapy.

Lodosyn is specifically used when a patient taking carbidopa-levodopa isn't getting enough daily carbidopa from that combination, or when a patient needs the two drugs individually titrated (adjusted) rather than taken as a fixed combination. Adding carbidopa helps reduce the nausea and vomiting that levodopa often causes and allows lower doses of levodopa to be used.

Most-Reported Side Effects for Carbidopa

From FAERS, the FDA’s public side-effect reporting system (52,609 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fall 4,954 reports
Hallucination 4,554 reports
Tremor 3,533 reports
Dyskinesia 3,174 reports
Dizziness 2,837 reports
See full Carbidopa 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 Carbidopa, 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 Carbidopa Together: Common Questions

Is it safe to take Niacinamide with Carbidopa?
We do not list a known interaction between Niacinamide and Carbidopa. 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 Carbidopa have any of the same side effects?
Yes — our sources link each of them separately to 10 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.
How was the Niacinamide and Carbidopa combination checked?
Interactions in our licensed database are recorded against drug classes. Carbidopa is filed under 3 classifications, and Niacinamide has documented interactions with 4 drug classes — none of Carbidopa'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 — Carbidopa 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 Carbidopa interact with any supplements?
Yes. Carbidopa has documented interactions with 21 supplements in our database — Niacinamide is not one of them. The Carbidopa 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 Carbidopa drug information The full plain-English guide to this medication Carbidopa supplement interactions Every supplement checked against Carbidopa, 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 Carbidopa and Niacinamide?

Our pharmacists answer your medication & supplement questions — free.

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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.