Thiamine + Phendimetrazine
Phendimetrazine brand names: Plegine, Metra, Weightrol.
We found no known interaction between Thiamine and Phendimetrazine 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.
Thiamine and Phendimetrazine
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 Phendimetrazine and Thiamine 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.
Thiamine safety at a glance
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.
Why No Interaction Is Listed for Phendimetrazine
Interactions in our licensed database are recorded against drug classes, not just single drug names. Phendimetrazine is filed under a single classification — oral drugs. Thiamine has documented interactions with 1 drug class — the most serious being trimethoprim (proloprim) (minor) — and none of Phendimetrazine’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.
Thiamine Does Interact With Other Medications
Thiamine has 3 minor known drug interactions in our database — Phendimetrazine isn’t one of them. If you take anything else, check it against the full list below.
Check Another of Your Medications Against Thiamine
We haven’t checked that one against Thiamine yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Thiamine. Pick one to open its full report.
Thiamine in Pregnancy & Breastfeeding
When used orally in dietary amounts of 1.4 mg daily. A tolerable upper intake level (UL) has not been established for healthy individuals.
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
What Phendimetrazine Is Prescribed For, and What Thiamine Has Been Studied For
These two come up together because they touch the same health topic — not because they do the same job. Phendimetrazine is a prescription medicine with approved uses on its FDA label. Thiamine is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.
Phendimetrazine is prescribed for: Phendimetrazine tartrate is used to help manage exogenous obesity (excess body weight from outside causes like diet and lifestyle) as a short-term addition to a calorie-restricted diet. It is intended for adults with a BMI of 30 or higher, or a BMI of 27 or higher when other risk factors — such as high blood pressure, diabetes, or high cholesterol — are also present. It is approved for use as monotherapy only, meaning it must not be combined with other weight-loss drugs or stimulants. Both the tablet form and the extended-release capsule form are approved for this purpose.
Read the rest of what Phendimetrazine is prescribed for
This medication is meant to be used for only a few weeks as part of a broader weight-management plan.
Thiamine has been studied for:
-
Diabetes studied, not established Thiamine has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows
Thiamine for diabetes
It is unclear if oral thiamine is beneficial for type 2 diabetes or gestational diabetes.
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 Phendimetrazine on your own; if you are taking Thiamine for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.
See Every Supplement That Interacts With Phendimetrazine
This page covers Thiamine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phendimetrazine page lists 17 supplements it has a documented interaction with, worst first, each one explained.
The most serious there right now: Activated Charcoal (major), Coffee Charcoal (moderate), European Mandrake (moderate), Glucomannan (moderate) and Guar Gum (moderate).
By severity: 1 major · 7 moderate · 9 minor.
From our pharmacist’s overview on the Phendimetrazine page
“Of the 17 supplements on file for phendimetrazine, an appetite-suppressant stimulant prescribed short term for weight loss, activated charcoal is the one that demands real caution. Charcoal binds medications in the gut and can sharply cut how much of a drug your body absorbs, leaving you with less appetite control than your prescriptio…”
Reviewed by 2 · Jul 18, 2026
Taking Thiamine as Part of a Dietary Supplement Product? Check It for Interactions
We hold 3 real supplement products containing Thiamine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Thiamine. Even though Thiamine itself has no known interaction with Phendimetrazine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:
Where Thiamine and Phendimetrazine 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.
#177 of 1,452 supplements looked up here in the last 7 days
#366 of 2,830 medications looked up here in the last 7 days
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 Thiamine reference on this page ↓
- Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Thiamine and Phendimetrazine 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.
About Thiamine
What is Thiamine?
- Preventing or treating thiamine deficiency
- Beriberi
- Wernicke-Korsakoff syndrome (alcohol-related)
- Supporting energy and nerve function
- General B-vitamin supplementation
Thiamine (vitamin B1) is an essential nutrient your body needs to turn food into energy and to keep your nerves and heart healthy. Most people get enough from food, but supplements are clearly useful for deficiency, certain medical conditions, and people with heavy alcohol use. Talk with your pharmacist or doctor before starting it, especially if you have a chronic illness.
Tablets, capsules, oral liquids, injectable solutions (prescription), part of B-complex and multivitamins
An interaction check asks whether these two react with each other — it does not ask whether Thiamine is a good idea for someone in your situation. Here is what our Thiamine record says about it on its own.
Thiamine: dosing
The right dose of thiamine depends on your age, health, and the reason you are taking it. There is a recommended daily intake for general nutrition, and higher amounts are sometimes used by doctors to treat a deficiency.For supplements, the best approach is to follow the directions on the product label and not exceed them without guidance.
From our Thiamine monograph — the full record covers uses, side effects and every documented interaction.
About Phendimetrazine
What Is Phendimetrazine Used For?
Brand names: Plegine, Metra, Weightrol
Phendimetrazine tartrate is used to help manage exogenous obesity (excess body weight from outside causes like diet and lifestyle) as a short-term addition to a calorie-restricted diet. It is intended for adults with a BMI of 30 or higher, or a BMI of 27 or higher when other risk factors — such as high blood pressure, diabetes, or high cholesterol — are also present.
It is approved for use as monotherapy only, meaning it must not be combined with other weight-loss drugs or stimulants. Both the tablet form and the extended-release capsule form are approved for this purpose. This medication is meant to be used for only a few weeks as part of a broader weight-management plan.
Other Drugs & Thiamine
Browse every other medication we’ve checked against Thiamine — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
3 interactions
No interaction 2,826 drugs checked — show the list
We also checked Thiamine against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Sertraline ›
- Testosterone ›
- Losartan Potassium ›
- Metoprolol ›
- Aspirin ›
- Ivermectin ›
- Rivaroxaban ›
- Rosuvastatin ›
- Escitalopram ›
- Acetaminophen ›
- Tadalafil ›
- Clopidogrel ›
- Atorvastatin ›
- Docusate ›
- Valacyclovir ›
- Abemaciclib ›
- Hydroxyurea ›
- Methamphetamine ›
- Ibuprofen ›
- Sumatriptan ›
- Semaglutide ›
- Warfarin Sodium ›
- Tirzepatide ›
- Prednisone ›
- Propranolol ›
- Bupropion ›
- Metformin ›
- Lisdexamfetamine ›
- Amoxicillin ›
- Lisinopril ›
- Acyclovir ›
- Bendamustine ›
- Amitriptyline ›
- Doxycycline ›
- Methotrexate ›
- Lamotrigine ›
- Fluoxetine ›
- Amphetamine ›
- Acetaminophen, Codeine ›
- Gabapentin ›
- Pregabalin ›
- Azithromycin ›
- Dextroamphetamine ›
- Isotretinoin ›
- Clonazepam ›
- Omeprazole ›
- Methylene Blue ›
- Quetiapine ›
- Amlodipine Besylate ›
- Duloxetine ›
- Letrozole ›
- Buspirone ›
- Citalopram ›
- Naproxen ›
- Ciprofloxacin ›
Showing the 60 most looked-up of 2,826 medications checked with no known interaction — see the full Thiamine list.
Thiamine References
The 7 references that drive our Thiamine 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.
- McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
- Yates AA, Schlicker SA, Suitor CW. Dietary reference intakes: The new basis for recommendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc 1998;98:699-706. PubMed
- 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
- Rogovik, A. L., Vohra, S., and Goldman, R. D. Safety considerations and potential interactions of vitamins: should vitamins be considered drugs? Ann.Pharmacother. 2010;44(2):311-324. PubMed
- Arruti N, Bernedo N, Audicana MT, Villarreal O, Uriel O, Muñoz D. Systemic allergic dermatitis caused by thiamine after iontophoresis. Contact Dermatitis. 2013 Dec;69(6):375-6. PubMed
- Thiamine hydrochloride injection package insert. Lake Zurich, IL: Fresenius Kabi, LLC; September 2019.
- Vora B, Wen A, Yee SW, et al. The Effect of Trimethoprim on Thiamine Absorption: A Transporter-Mediated Drug-Nutrient Interaction. Clin Pharmacol Ther 2023;114(2):381-392.
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.
Taking Thiamine and Phendimetrazine Together: Common Questions
Is it safe to take Thiamine with Phendimetrazine?
Are Thiamine and Phendimetrazine used for the same thing?
How was the Thiamine and Phendimetrazine combination checked?
Does Thiamine interact with any other medications?
Does Phendimetrazine interact with any supplements?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Keep Exploring
Still Have a Question About Phendimetrazine and Thiamine?
Our pharmacists answer your medication & supplement questions — free.
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.