Drug & supplement interaction

Plant Sterols + 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 20, 2026
The bottom line No known interaction

We found no known interaction between Plant Sterols 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

Plant Sterols 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 Plant Sterols 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Plant Sterols at all — not against Phentermine, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Plant Sterols safety at a glance

Plant Sterols overall Generally safe Generally well tolerated at typical food and supplement amounts for most adults.
Pregnancy Use caution Safety of concentrated supplements during pregnancy is not well studied, so use caution and check with your doctor.
Breastfeeding Use caution There is limited information on concentrated supplements during breastfeeding, so caution is advised.

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

Still wondering about combining Phentermine and Plant Sterols? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Plant Sterols and Phentermine 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.

  • Stomach upset / Diarrhea Additional detail

    Plant Sterols

    “Abdominal discomfort has occurred in one child in a clinical trial of oral plant sterols. Because plant sterols decrease cholesterol absorption in the gut, there is concern that they might produce some gastrointestinal symptoms like diarrhea and excess amounts of fat in the stool (steatorrhea), although these adverse effects have not been reported in clinical research.”

    Plant Sterols · Natural Medicines adverse-effect record, reported in diarrhea.

    1 source cited
    1. 35106. Guardamagna, O., Abello, F., Baracco, V., Federici, G., Bertucci, P., Mozzi, A., Mannucci, L., Gnasso, A., and Cortese, C. Primary hyperlipidemias in children: effect of plant sterol supplementation on plasma lipids and markers of cholesterol synthesis a

    Phentermine

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

Reported for Plant Sterols but not commonly for Phentermine: a skin rash and acne.

Effects for Phentermine come from the ADVERSE REACTIONS section of its FDA label; effects for Plant Sterols 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.

Overlapping uses

What Phentermine Is Prescribed For, and What Plant Sterols Has Been Studied For

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

Phentermine is prescribed for: 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.

Read the rest of what Phentermine is prescribed for

Treatment is intended to last only a few weeks.

Plant Sterols has been studied for:

  • Obesity studied, not established Plant Sterols has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Plant Sterols for obesity

    It is unclear if oral plant sterols are beneficial for obesity.

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 Phentermine on your own; if you are taking Plant Sterols for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Plant Sterols 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 Plant Sterols 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 Plant Sterols 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 Plant Sterols as Part of a Dietary Supplement Product? Check It for Interactions

We hold 28 real supplement products containing Plant Sterols, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Plant Sterols. Even though Plant Sterols 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 Plant Sterols 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 Plant Sterols
Steady interest

#1,154 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phentermine
Top 10%

#210 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 Plant Sterols reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Plant Sterols and Phentermine 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 Plant Sterols

What is Plant Sterols?

  • High cholesterol
  • Heart health support
  • Lowering LDL cholesterol

Plant sterols (and their close relatives, plant stanols) are natural compounds found in plants that can modestly lower LDL ('bad') cholesterol when taken regularly in adequate amounts, usually through fortified foods or supplements. They are widely considered a useful add-on to a heart-healthy diet, but they are not a replacement for prescribed cholesterol medicine. Talk with your pharmacist or doctor before starting them, especially if you take cholesterol drugs.

Sterols extracted from plant oils, nuts, seeds, grains, and legumes · Capsules, softgels, fortified margarine/spreads, fortified yogurt and milk, powders

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

Plant Sterols: dosing

There is no single official dose for everyone, but cholesterol-lowering benefits are generally seen only when enough is taken consistently each day, usually spread across meals. Taking them with food is often recommended, since they work by affecting how cholesterol is absorbed during digestion.The best approach is to follow the directions on your specific product label, since fortified foods and supplements vary in strength.

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

Read the full Plant Sterols 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 & Plant Sterols

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Plant Sterols list.

See the full Plant Sterols interactions page
See every supplement checked against Phentermine, ranked by severity
Evidence & sources

Plant Sterols References

The 3 references that drive our Plant Sterols 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. Guardamagna, O., Abello, F., Baracco, V., Federici, G., Bertucci, P., Mozzi, A., Mannucci, L., Gnasso, A., and Cortese, C. Primary hyperlipidemias in children: effect of plant sterol supplementation on plasma lipids and markers of cholesterol synthesis a
  2. Haque Hussain SS, Weir J, Roberts N. Severe dermatitis secondary to plant sterol supplements. Clin Exp Dermatol. 2009 Oct;34(7):e276-7. PubMed
  3. Xue P, Wang Y, Chen Y, et al. A Case of Peripheral Precocious Puberty May Be Caused by a Diet Containing Phytosterols in a 20-Month-Old Boy. Horm Res Paediatr 2022;95(5):484-491. 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 Plant Sterols and Phentermine Together: Common Questions

Is it safe to take Plant Sterols with Phentermine?
We do not list a known interaction between Plant Sterols 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 Plant Sterols and Phentermine have any of the same side effects?
Yes — our sources link each of them separately to 2 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 Plant Sterols and Phentermine 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 Plant Sterols in each. That is a conversation for your prescriber, especially if Phentermine is being adjusted to a target.
Does Phentermine interact with any supplements?
Yes. Phentermine has documented interactions with 61 supplements in our database — Plant Sterols 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

Plant Sterols 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 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phentermine and Plant Sterols?

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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.