Drug & supplement interaction

Propionyl-l-carnitine + Phentermine

Phentermine brand names: Adipex-P, Fastin, T Diet, Phentride, Obenix, and others.

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 Propionyl-l-carnitine and Phentermine 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

Propionyl-l-carnitine and Phentermine

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 Phentermine and Propionyl-l-carnitine 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.

Propionyl-l-carnitine safety at a glance

Propionyl-l-carnit... overall Use caution Generally well tolerated for short-term use, but talk to a healthcare provider first.
Pregnancy Avoid Safety has not been established, so it is best avoided during pregnancy.
Breastfeeding Avoid Not enough safety data is available, so avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Phentermine and Propionyl-l-carnitine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phentermine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phentermine is filed under 2 classifications — stimulant drugs, oral drugs. Propionyl-l-carnitine has documented interactions with 3 drug classes — the most serious being acenocoumarol (sintrom) (moderate), thyroid hormone (moderate) and warfarin (coumadin) (moderate) — and none of Phentermine’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

Propionyl-l-carnitine Does Interact With Other Medications

Propionyl-l-carnitine has 19 moderate known drug interactions in our database — Phentermine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 19 No known interaction 2,811 (incl. Phentermine)
Taking anything else?

Check Another of Your Medications Against Propionyl-l-carnitine

Covers the 2,830 medications we’ve checked against Propionyl-l-carnitine. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Propionyl-l-carnitine and Phentermine May Share a Side Effect

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.

  • Diarrhea Additional detail

    Propionyl-l-carnitine

    “Orally, nausea, vomiting, diarrhea, and gastric pain have been reported with propionyl-L-carnitine use.”

    Propionyl-l-carnitine · Natural Medicines adverse-effect record, reported in diarrhea.

    6 sources cited
    1. 1579. Cherchi A, Lai C, Onnis E, et al. Propionyl carnitine in stable effort angina. Cardiovasc Drugs Ther 1990;4:481-6. PubMed
    2. 1580. Bartels GL, Remme WJ, den Hartog FR, et al. Additional anti-ischemic effects of long-term L-propionylcarnitine in anginal patients treated with conventional antianginal therapy. Cardiovasc Drugs Ther 1995;9:749-53.
    3. 1582. Caponnetto S, Canale C, Masperone MA, et al. Efficacy of L-propionylcarnitine treatment in patients with left ventricular dysfunction. Eur Heart J 1994;15:1267-73. PubMed
    4. 12682. Gentile V, Vicini P, Prigiotti G, et al. Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes. Curr Med Res Opin 2004;20:1377-84. PubMed
    5. 94439. Brass EP, Koster D, Hiatt WR, Amato A. A systematic review and meta-analysis of propionyl-L-carnitine effects on exercise performance in patients with claudication. Vasc Med 2013;18:3-12.
    6. 94443. Hiatt WR, Creager MA, Amato A, Brass EP. Effect of propionyl-L-carnitine on a background of monitored exercise in patients with claudication secondary to peripheral artery disease. J Cardiopulm Rehabil Prev 2011;31:125-32. PubMed

    Phentermine

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

Reported for Propionyl-l-carnitine but not commonly for Phentermine: back pain, vomiting and nausea.

Effects for Phentermine come from the ADVERSE REACTIONS section of its FDA label; effects for Propionyl-l-carnitine 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.

From our Q&A

Questions About Propionyl-l-carnitine or Phentermine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Propionyl-l-carnitine or Phentermine, 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 Phentermine

This page covers Propionyl-l-carnitine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phentermine page lists 61 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Peyote (major), Rauvolfia Vomitoria (major) and Sida Cordifolia (major).

By severity: 5 major · 43 moderate · 13 minor.

From our pharmacist’s overview on the Phentermine page

“Ephedra is the pairing I most want anyone taking phentermine (Adipex-P) to know about. Phentermine is itself a stimulant appetite suppressant that raises heart rate and blood pressure, and ephedra piles the same cardiovascular strain on top of it.”

Reviewed by 2 · Jul 18, 2026

Open the Phentermine interaction page

One more smart check

Taking Propionyl-l-carnitine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 57 real supplement products containing Propionyl-l-carnitine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Propionyl-l-carnitine. Even though Propionyl-l-carnitine itself has no known interaction with Phentermine, 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 Propionyl-l-carnitine and Phentermine 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 Propionyl-l-carnitine
Steady interest

#1,251 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phentermine
Top 10%

#282 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 Propionyl-l-carnitine reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Propionyl-l-carnitine and Phentermine records this page draws on were last updated July 11, 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 Propionyl-l-carnitine

What is Propionyl-l-carnitine?

  • Peripheral artery disease and leg pain
  • Heart and circulation support
  • Energy and exercise performance
  • Erectile dysfunction
  • Diabetic nerve pain

Propionyl-l-carnitine is a form of the amino acid derivative carnitine that the body uses to help turn fat into energy, and it is studied mostly for circulation problems like peripheral artery disease. Some evidence suggests it may help walking distance in people with poor leg circulation, but results are mixed and it is not a substitute for standard medical care. Talk to a pharmacist or doctor before using it, especially if you have a medical condition or take other medicines.

Capsules, tablets, oral powder

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

Propionyl-l-carnitine: dosing

There is no single official dose of PLC for supplement use, and the right amount can depend on the condition being studied and the specific product. They can help you decide whether PLC is appropriate for you and what amount makes sense.Do not assume more is better. Higher doses raise the chance of side effects without guaranteeing more benefit.

From our Propionyl-l-carnitine monograph — the full record covers uses, side effects and every documented interaction.

Read the full Propionyl-l-carnitine monograph & all interactions
Medication

About Phentermine

What Is Phentermine Used For?

Brand names: Adipex-P, Fastin, T Diet, Phentride, Obenix, Pbc Phentride, Pbw Phentride, Phentrol #3, Ionamin, Phentrol #6, Phentrol #2, Phentrol #5, Phentrol, Obermine, Phentermine, Suprenza

Phentermine is approved as a short-term addition to a weight-loss program — not a standalone treatment. It is used alongside reduced-calorie eating, increased physical activity, and behavior changes to help manage obesity in adults whose body mass index (BMI) is 30 kg/m² or higher, or 27 kg/m² or higher when other risk factors such as controlled high blood pressure, diabetes, or high cholesterol (hyperlipidemia) are also present.

All available phentermine products — including Adipex-P, Lomaira, and various generic capsules and tablets — share this same FDA-approved use. Lomaira tablets are specifically dosed to be taken three times daily before meals, while other formulations are generally taken once daily. Treatment is intended to last only a few weeks.

See full Phentermine drug information
Keep checking

Other Drugs & Propionyl-l-carnitine

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

0Major
19Moderate
0Minor
2,810No known interaction
19 Moderate 2,810 No interaction
Moderate

19 interactions

No interaction 2,810 drugs checked — show the list

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

Showing the 60 most looked-up of 2,810 medications checked with no known interaction — see the full Propionyl-l-carnitine list.

See the full Propionyl-l-carnitine interactions page
See every supplement checked against Phentermine, ranked by severity
Evidence & sources

Propionyl-l-carnitine References

The 12 references that drive our Propionyl-l-carnitine 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. Cherchi A, Lai C, Onnis E, et al. Propionyl carnitine in stable effort angina. Cardiovasc Drugs Ther 1990;4:481-6. PubMed
  2. Bartels GL, Remme WJ, den Hartog FR, et al. Additional anti-ischemic effects of long-term L-propionylcarnitine in anginal patients treated with conventional antianginal therapy. Cardiovasc Drugs Ther 1995;9:749-53.
  3. Caponnetto S, Canale C, Masperone MA, et al. Efficacy of L-propionylcarnitine treatment in patients with left ventricular dysfunction. Eur Heart J 1994;15:1267-73. PubMed
  4. Benvenga S, Ruggeri RM, Russo A, et al. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Meta
  5. Martinez E, Domingo P, Roca-Cusachs A. Potentiation of acenocoumarol action by L-carnitine. J Intern Med 1993;233:94.
  6. Bachmann HU, Hoffmann A. Interaction of food supplement L-carnitine with oral anticoagulant acenocoumarol. Swiss Med Wkly 2004;134:385. PubMed
  7. Gentile V, Vicini P, Prigiotti G, et al. Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes. Curr Med Res Opin 2004;20:1377-84. PubMed
  8. 12761 Benvenga S, Amato A, Calvani M, Trimarchi F. Effects of carnitine on thyroid hormone action. Ann N Y Acad Sci 2004;1033:158-67. PubMed
  9. Brass EP, Koster D, Hiatt WR, Amato A. A systematic review and meta-analysis of propionyl-L-carnitine effects on exercise performance in patients with claudication. Vasc Med 2013;18:3-12.
  10. Hiatt WR, Creager MA, Amato A, Brass EP. Effect of propionyl-L-carnitine on a background of monitored exercise in patients with claudication secondary to peripheral artery disease. J Cardiopulm Rehabil Prev 2011;31:125-32. PubMed
  11. Jacobs PL, Goldstein ER, Blackburn W, et al. Glycine propionyl-L-carnitine produces enhanced anaerobic work capacity with reduced lactate accumulation in resistance trained males. J Int Soc Sports Nutr 2009;6:9. PubMed
  12. Jacobs PL, Goldstein ER. Long-term glycine propionyl-l-carnitine supplementation and paradoxical effects on repeated anaerobic sprint performance. J Int Soc Sports Nutr 2010;7:35.

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 Propionyl-l-carnitine and Phentermine Together: Common Questions

Is it safe to take Propionyl-l-carnitine with Phentermine?
We do not list a known interaction between Propionyl-l-carnitine and Phentermine. 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 Propionyl-l-carnitine and Phentermine have any of the same side effects?
Yes — our sources link each of them separately to one 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 Propionyl-l-carnitine and Phentermine combination checked?
Interactions in our licensed database are recorded against drug classes. Phentermine is filed under 2 classifications, and Propionyl-l-carnitine has documented interactions with 3 drug classes — none of Phentermine'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 Propionyl-l-carnitine interact with any other medications?
Yes. Propionyl-l-carnitine has 19 documented drug interactions in our database — Phentermine 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 Phentermine interact with any supplements?
Yes. Phentermine has documented interactions with 61 supplements in our database — Propionyl-l-carnitine is not one of them. The Phentermine 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

Propionyl-l-carnitine monograph Uses, safety profile, and every drug interaction in one place Phentermine drug information The full plain-English guide to this medication Phentermine supplement interactions Every supplement checked against Phentermine, 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 12 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phentermine and Propionyl-l-carnitine?

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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.