Drug & supplement interaction

Beta-sitosterol + Olaparib

Olaparib brand name: Lynparza.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 20, 2026

The bottom line No known interaction

We found no known interaction between Beta-sitosterol and Olaparib 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

Beta-sitosterol and Olaparib

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 Olaparib and Beta-sitosterol 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 Beta-sitosterol at all — not against Olaparib, 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.

Beta-sitosterol safety at a glance

Beta-sitosterol overall Use caution Generally well tolerated for most adults when used short-term, but check with a healthcare provider first.

Pregnancy Avoid There is not enough safety data, so it is best to avoid supplemental use during pregnancy.

Breastfeeding Avoid There is not enough safety data, so it is best to avoid supplemental use while breastfeeding.

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

Still wondering about combining Olaparib and Beta-sitosterol? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

What to actually watch for

No Interaction Found — But Data Suggests Beta-sitosterol and Olaparib 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 / Reduced appetite Additional detail
Beta-sitosterol
“Orally, beta-sitosterol can cause nausea, indigestion, gas, diarrhea, or constipation. Beta-sitosterol can also reduce the appetite. There is a case report of acute pancreatitis thought to be associated with taking beta-sitosterol in a 57-year-old male.”

Beta-sitosterol · Natural Medicines adverse-effect record, reported in constipation.
5 sources cited

5327. Berges RR, Windeler J, Trampisch HJ, et al. Randomised, placebo-controlled, double-blind clinical trial of beta-sitosterol in patients with benign prostatic hyperplasia. Beta-sitosterol Study Group. Lancet 1995;345:1529-32.

5328. Klippel KF, Hiltl DM, Schipp B. A multicentric, placebo-controlled, double-blind clinical trial of beta-sitosterol (phytosterol) for the treatment of benign prostatic hyperplasia. Br J Urol 1997;80:427-32.

5334. Becker M, Staab D, Von Bergman K. Long-term treatment of severe familial hypercholesterolemia in children: effect of sitosterol and bezafibrate. Pediatrics 1992;89:138-42. DOI

106080. Lorenze A, Hsueh W, Nasr J. Beta-sitosterol-induced acute pancreatitis: A case report and review of the literature. Cureus. 2020;12(3):e7407. PubMed

15550. Prager N, Bickett K, French N, Marcovici G. A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia. J Altern Complement Med 2002
Olaparib

Listed in the ADVERSE REACTIONS section of the FDA label for Olaparib. Read the label on DailyMed ›
Stomach upset / Constipation / Nausea / Diarrhea reported in 8.8% of FDA reports for Olaparib Additional detail

Beta-sitosterol

“Orally, beta-sitosterol is generally well tolerated. Topically, beta-sitosterol seems to be well tolerated.

Most Common Adverse Effects:

Orally: Constipation, diarrhea, gas, indigestion, and nausea.”

Beta-sitosterol · Natural Medicines adverse-effect record, reported in constipation.

Olaparib

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

Reported for Beta-sitosterol but not commonly for Olaparib: erection problems, pancreatitis, a change in sex drive and acne.

Effects for Olaparib come from the ADVERSE REACTIONS section of its FDA label; effects for Beta-sitosterol come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 20,798 voluntary FDA FAERS reports for Olaparib 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.

Overlapping uses

What Olaparib Is Prescribed For, and What Beta-sitosterol Has Been Studied For

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

Olaparib is prescribed for: Lynparza (olaparib) is used to treat adults with certain ovarian, fallopian tube, or primary peritoneal cancers that carry BRCA or other DNA-repair gene mutations — both as a maintenance therapy after platinum-based chemotherapy (including in combination with bevacizumab for some patients) and for recurrent disease. It is also approved for HER2-negative breast cancer with a germline BRCA mutation, both in early high-risk disease (adjuvant setting) and in metastatic disease. Lynparza is additionally used as maintenance therapy for adults with germline BRCA-mutated metastatic pancreatic adenocarcinoma whose disease has not progressed on first-line platinum-based chemotherapy, and for adults with certain gene-mutated metastatic castration-resistant prostate cancer — either alone (after prior enzalutamide or abiraterone) or in combination with abiraterone and prednisone or prednisolone. All uses require testing for specific genetic mutations using an FDA-approved companion diagnostic before starting treatment.

Beta-sitosterol has been studied for:

Cancer studied, not established Beta-sitosterol has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

Beta-sitosterol for cancer

It is unclear if dietary beta-sitosterol is beneficial for cancer prevention.

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 Olaparib on your own; if you are taking Beta-sitosterol for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

Everything else you take

See Every Supplement That Interacts With Olaparib

This page covers Beta-sitosterol only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Olaparib page lists 138 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Adrafinil (moderate).

By severity: 3 major · 94 moderate · 41 minor.

From our pharmacist’s overview on the Olaparib page

“Grapefruit is the first thing to drop if you take Olaparib (Lynparza). It blocks CYP3A4, the liver enzyme that clears this cancer drug, so levels can climb and side effects with them.”

Reviewed by 2 · Jul 18, 2026

Open the Olaparib interaction page

One more smart check

Taking Beta-sitosterol as Part of a Dietary Supplement Product? Check It for Interactions

We hold 7 real supplement products containing Beta-sitosterol, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Beta-sitosterol. Even though Beta-sitosterol itself has no known interaction with Olaparib, 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 Beta-sitosterol and Olaparib 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 Beta-sitosterol

Top 25%

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

29 days ago today

Medication Olaparib

Steady interest

#1,512 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 Beta-sitosterol reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Beta-sitosterol and Olaparib 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 Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Beta-sitosterol

What is Beta-sitosterol?

High cholesterol
Enlarged prostate (BPH)
Heart health
Immune support
Hair loss

Beta-sitosterol is a plant sterol that may modestly lower LDL ('bad') cholesterol and may help ease urinary symptoms from an enlarged prostate. Evidence is moderate for these uses and weaker for others, and it is generally well tolerated, but you should talk with your pharmacist or doctor before starting it.

Plant sterol found in seeds, nuts, vegetable oils, and many plants · Capsules, tablets, softgels, and fortified foods

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

Beta-sitosterol: dosing

There is no single official dose of beta-sitosterol for all uses. The amount used in studies varies depending on the condition being studied, and product strengths differ between brands.The best approach is to follow the directions on the product label and not take more than recommended.

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

Read the full Beta-sitosterol monograph & all interactions

Medication

About Olaparib

What Is Olaparib Used For?

Brand name: Lynparza

Lynparza (olaparib) is used to treat adults with certain ovarian, fallopian tube, or primary peritoneal cancers that carry BRCA or other DNA-repair gene mutations — both as a maintenance therapy after platinum-based chemotherapy (including in combination with bevacizumab for some patients) and for recurrent disease. It is also approved for HER2-negative breast cancer with a germline BRCA mutation, both in early high-risk disease (adjuvant setting) and in metastatic disease.

Lynparza is additionally used as maintenance therapy for adults with germline BRCA-mutated metastatic pancreatic adenocarcinoma whose disease has not progressed on first-line platinum-based chemotherapy, and for adults with certain gene-mutated metastatic castration-resistant prostate cancer — either alone (after prior enzalutamide or abiraterone) or in combination with abiraterone and prednisone or prednisolone. All uses require testing for specific genetic mutations using an FDA-approved companion diagnostic before starting treatment.

Most-Reported Side Effects for Olaparib

From FAERS, the FDA’s public side-effect reporting system (20,798 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Malignant neoplasm progression 2,063 reports

Nausea 1,827 reports

Fatigue 1,762 reports

Anemia 1,622 reports

Vomiting 724 reports

See full Olaparib drug information

Keep checking

Other Drugs & Beta-sitosterol

Browse every other medication we’ve checked against Beta-sitosterol — 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 Beta-sitosterol 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 Beta-sitosterol list.

See the full Beta-sitosterol interactions page

See every supplement checked against Olaparib, ranked by severity

Evidence & sources

Beta-sitosterol References

The 7 references that drive our Beta-sitosterol 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.

Berges RR, Windeler J, Trampisch HJ, et al. Randomised, placebo-controlled, double-blind clinical trial of beta-sitosterol in patients with benign prostatic hyperplasia. Beta-sitosterol Study Group. Lancet 1995;345:1529-32.
Klippel KF, Hiltl DM, Schipp B. A multicentric, placebo-controlled, double-blind clinical trial of beta-sitosterol (phytosterol) for the treatment of benign prostatic hyperplasia. Br J Urol 1997;80:427-32.
Wilt TJ, MacDonald R, Ishani A. beta-sitosterol for the treatment of benign prostatic hyperplasia: a systematic review. BJU Int 1999;83:976-83. PubMed
Oster P, Schlierf G, Heuck CC, et al. [Sitosterol in familial hyperlipoproteinemia type II. A randomized, double-blind, cross-over study]. Dtsch Med Wochenschr 1976;101:1308-11.
Becker M, Staab D, Von Bergman K. Long-term treatment of severe familial hypercholesterolemia in children: effect of sitosterol and bezafibrate. Pediatrics 1992;89:138-42. DOI
Prager N, Bickett K, French N, Marcovici G. A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia. J Altern Complement Med 2002
Lorenze A, Hsueh W, Nasr J. Beta-sitosterol-induced acute pancreatitis: A case report and review of the literature. Cureus. 2020;12(3):e7407. 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 Beta-sitosterol and Olaparib Together: Common Questions

Is it safe to take Beta-sitosterol with Olaparib?

We do not list a known interaction between Beta-sitosterol and Olaparib. 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 Beta-sitosterol and Olaparib have any of the same side effects?

Yes — our sources link each of them separately to 6 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 Beta-sitosterol and Olaparib 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 Beta-sitosterol in each. That is a conversation for your prescriber, especially if Olaparib is being adjusted to a target.

Does Olaparib interact with any supplements?

Yes. Olaparib has documented interactions with 138 supplements in our database — Beta-sitosterol is not one of them. The Olaparib 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

Beta-sitosterol monograph Uses, safety profile, and every drug interaction in one place Olaparib drug information The full plain-English guide to this medication Olaparib supplement interactions Every supplement checked against Olaparib, 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 7 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Olaparib and Beta-sitosterol?

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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.