Drug & supplement interaction

Black Psyllium + Olanzapine

Olanzapine brand name: Zyprexa.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Olanzapine falls into 2 drug categories that Black Psyllium can interact with; the most serious is rated moderate. Theoretically, taking black psyllium at the same time as olanzapine might reduce olanzapine absorption.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Black Psyllium and Olanzapine

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Black Psyllium interacts with whole categories of medication. Olanzapine falls into 2 of those categories, so it can interact with Black Psyllium in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

OLANZAPINE (Zyprexa)

1 of 2
Theoretically, taking black psyllium at the same time as olanzapine might reduce olanzapine absorption.
The fiber in black psyllium might decrease the absorption of olanzapine. A single case report describes a reduction in the effectiveness of olanzapine when it was concomitantly administered with an unspecified type of psyllium 3 grams orally twice daily. This effect was reversed when psyllium was stopped.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with black psyllium and your olanzapine. That thick fiber gel psyllium forms in your gut can grab onto some medications and keep them from being fully absorbed. So the worry isn't a buildup, it's the opposite. Less olanzapine may get into your system, which could make it work less well. For something treating schizophrenia or bipolar disorder, that might show up as your symptoms creeping back, like more anxiety, mood swings, or trouble sleeping.

I want to be honest about how shaky this is. It comes from a single case report, so it's more of a theoretical caution than a proven problem. An easy fix many folks use is simply spacing them apart, taking your olanzapine and your psyllium a few hours from each other. Run that timing by your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Merrick C, Madden CA, Capurso NA. A Case of Blunted Orally Disintegrating Olanzapine Effect Due to Coadministered Psyllium. J Clin Psychiatry 2021;82(2):20cr13633. PubMed
Minor

ORAL DRUGS

2 of 2

Why this applies to Olanzapine

Olanzapine falls under ORAL DRUGS — the group Black Psyllium interacts with.

Theoretically, psyllium might increase, decrease, or have no effect on the absorption of oral drugs.
Psyllium seems to have variable effects on drug absorption. To avoid changes in absorption, take psyllium 30-60 minutes after oral medications. Animal research shows that blond psyllium delays and increases the absorption of metformin and ethinyl estradiol. Case reports and animal research suggest that blond psyllium might reduce absorption of lithium, digoxin, olanzapine, and carbamazepine. Finally, some pharmacokinetic studies show that psyllium does not affect the absorption of levothyroxine or warfarin. Although many of these studies evaluated blond psyllium, the fiber content in black psyllium may have similar effects.
Severity Minor Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: that thick fiber gel from black psyllium can grab onto your olanzapine in the gut and carry some of it through before your body fully absorbs it. In plain terms, you might soak up a little less of your dose. For a medication that steadies mood and thinking in schizophrenia or bipolar disorder, getting less than expected could mean it doesn't work as well for you.

The good news is this is rated minor and the evidence is fairly weak (mostly case reports and animal data), so don't panic. An easy fix many pharmacists suggest is spacing them out, taking psyllium about 30 to 60 minutes after your olanzapine. Please run the timing past your own pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  3. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
  4. Robinson DS, Benjamin DM, McCormack JJ. Interaction of warfarin and nonsystemic gastrointestinal drugs. Clin Pharmacol Ther 1971;12:491-5. PubMed
  5. Garcia JJ, Fernandez N, Diez MJ, et al. Influence of two dietary fibers in the oral bioavailability and other pharmacokinetic parameters of ethinyloestradiol. Contraception 2000;62:253-7. PubMed
  6. Semen plantaginis in: WHO Monographs on Selected Medicinal Plants, volume 1. World Health Organization, Geneva, 1999. Available at http://apps.who.int/medicinedocs/en/d/Js2200e/. Accessed November 26, 1026.
  7. Diez R, Garcia JJ, Diez MJ, Sierra M, Sahagun AM, Fernandez N. Influence of Plantago ovata husk (dietary fiber) on the bioavailability and other pharmacokinetic parameters of metformin in diabetic rabbits. BMC Complement Altern Med. 2017 Jun 7;17(1):298. PubMed
  8. Chiu AC, Sherman SI. Effects of pharmacological fiber supplements on levothyroxine absorption. Thyroid. 1998;8(8):667-71. PubMed
  9. Merrick C, Madden CA, Capurso NA. A Case of Blunted Orally Disintegrating Olanzapine Effect Due to Coadministered Psyllium. J Clin Psychiatry 2021;82(2):20cr13633. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Black Psyllium Also Interacts With Other Medications

Black Psyllium has 22 moderate, 2,002 minor known drug interactions in our database — the Olanzapine one above is among them. If you take anything else, check it against the full list below.

Moderate 22 Minor 2,002 No known interaction 806 (incl. Olanzapine)
Taking anything else?

Check Another of Your Medications Against Black Psyllium

Covers the 2,830 medications we’ve checked against Black Psyllium. Pick one to open its full report.

From our Q&A

Questions About Black Psyllium or Olanzapine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Psyllium or Olanzapine, 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 Olanzapine

This page covers Black Psyllium only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Olanzapine page lists 160 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Indian Snakeroot (major), Lithium (major), Rauvolfia Vomitoria (major) and 1,3-dmaa (moderate).

By severity: 4 major · 118 moderate · 38 minor.

From our pharmacist’s overview on the Olanzapine page

“Olanzapine (Zyprexa) is an antipsychotic prescribed for schizophrenia and bipolar disorder, and adding supplements to it warrants genuine care. Four of the 160 ingredients on file rate major, and those four deserve your attention before anything else: lithium supplements raise the risk of serotonin syndrome, activated charcoal can trap…”

Reviewed by 2 · Jul 18, 2026

Open the Olanzapine interaction page

One more smart check

Taking Black Psyllium as Part of a Dietary Supplement Product? Check It for Interactions

We hold 5 real supplement products containing Black Psyllium, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Psyllium. Your product may carry other ingredients that interact with Olanzapine too, on top of Black Psyllium — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Psyllium and Olanzapine 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 Black Psyllium
Top half

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

29 days ago today
Medication Olanzapine
Top 25%

#289 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.

Supplement

About Black Psyllium

What is Black Psyllium?

Black Psyllium
  • Constipation
  • Diarrhea
  • High cholesterol
  • Digestive health
  • Blood sugar support
  • Weight management

Black psyllium is a soluble-fiber supplement made from the seeds of a Plantago plant, used mostly to ease constipation and support digestive health. It is best known and most studied for relieving constipation and may modestly help lower cholesterol, but it must always be taken with plenty of water. Talk with your pharmacist or doctor before starting, especially if you have swallowing problems or bowel disorders.

Read the full Black Psyllium monograph & all interactions
Medication

About Olanzapine

What Is Olanzapine Used For?

Brand name: Zyprexa

Olanzapine treats schizophrenia and the manic or mixed episodes of bipolar I disorder in both adults and adolescents (ages 13–17). It can also be used alongside valproate or lithium to treat manic or mixed episodes in adults. When combined with fluoxetine, olanzapine tablets and orally disintegrating tablets are used to treat depressive episodes associated with bipolar I disorder and treatment-resistant depression in adults.

Olanzapine intramuscular injection (short-acting) is used by healthcare providers to quickly calm acute agitation in adults with schizophrenia or bipolar I mania. Zyprexa Relprevv — a separate, long-acting intramuscular formulation available only through a restricted program — is indicated specifically for the treatment of schizophrenia in adults.

See full Olanzapine drug information
Keep checking

Other Drugs & Black Psyllium

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

0Major
22Moderate
2,002Minor
805No known interaction
22 Moderate 2,002 Minor 805 No interaction
Moderate

22 interactions

Minor

2,002 interactions

Showing 60 of 2,002 minor interactions — see all 2,002 on the Black Psyllium page.

No interaction 805 drugs checked — show the list

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

Showing the 60 most looked-up of 805 medications checked with no known interaction — see the full Black Psyllium list.

See the full Black Psyllium interactions page
See every supplement checked against Olanzapine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Black Psyllium monograph › Uses, safety, and every drug interaction in one place Olanzapine supplement interactions › Every supplement checked against Olanzapine, ranked by severity Olanzapine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Black Psyllium and Olanzapine Together: Common Questions

Can you take Black Psyllium with Olanzapine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Black Psyllium and Olanzapine?
Olanzapine belongs to more than one drug category, and Black Psyllium interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Black Psyllium and Olanzapine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Olanzapine and Black Psyllium?

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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.