Drug & supplement interaction

Castor Bean + Metformin

Metformin brand names: Glucophage, Metformin.

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 Castor Bean and Metformin 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

Castor Bean and Metformin

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 Metformin and Castor Bean 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.

Castor Bean safety at a glance

Castor Bean overall Use caution Properly processed castor oil is generally safe in small amounts, but raw seeds are highly toxic.
Pregnancy Possibly Safe When castor oil is used orally in pregnant women at term. Although there have been reports of fetal meconium passage being more common with castor oil use in pr... Read the full pregnancy detail
Breastfeeding Use caution There is limited safety information, so avoid or use only under professional guidance.

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.

Still wondering about combining Metformin and Castor Bean? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metformin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metformin is filed under 5 classifications — including organic cation transporter 2 (oct2) substrates, antidiabetes drugs, oral drugs. Castor Bean has documented interactions with 1 drug class — the most serious being diuretic drugs (moderate) — and none of Metformin’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

Castor Bean Does Interact With Other Medications

Castor Bean has 75 moderate known drug interactions in our database — Metformin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 75 No known interaction 2,755 (incl. Metformin)
Taking anything else?

Check Another of Your Medications Against Castor Bean

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

What to actually watch for

No Interaction Found — But Data Suggests Castor Bean and Metformin 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. One of them is worth acting on rather than waiting out — marked below.

  • Shortness of breath Worth acting on Additional detail

    Castor Bean

    “After inhalation, ricin, the toxic constituent of the castor seed hull, typically causes respiratory illness within 8 hours, but symptoms may be delayed. Symptoms include cough, dyspnea, and fever. Progression to respiratory distress and death can occur.”

    Castor Bean · Natural Medicines adverse-effect record, reported in acute respiratory distress syndrome (ards).

    1 source cited
    1. 13715. Audi J, Belson M, Patel M, et al. Ricin poisoning: a comprehensive review. JAMA 2005;294:2342-51.

    Metformin

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

  • Stomach upset / Diarrhea / Vomiting Additional detail

    Castor Bean

    “Orally, castor oil, like all stimulant laxatives, can cause abdominal discomfort, cramping, nausea, and faintness (15,272,40183,40186,40187,40192,40177,40185,40188,40163). Nausea can also occur because of the unpleasant taste of castor oil. Using flavored products might reduce this effect. Castor oil can also cause fluid and electrolyte loss, particularly potassium, which can result in hypokalemia.”

    Castor Bean · Natural Medicines adverse-effect record, reported in diarrhea.

    6 sources cited
    1. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    2. 272. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
    3. 40183. Kris, M. G., Gralla, R. J., Clark, R. A., Tyson, L. B., and Groshen, S. Control of chemotherapy-induced diarrhea with the synthetic enkephalin BW942C: a randomized trial with placebo in patients receiving cisplatin. J Clin.Oncol. 1988;6(4):663-668. PubMed
    4. 40186. Ryan, J., Leighton, J., Kirksey, D., and McMahon, G. Evaluation of an enkephalin analog in men with castor oil-induced diarrhea. Clin.Pharmacol.Ther. 1986;39(1):40-42. PubMed
    5. 40187. Dodds, W. J., Scanlon, G. T., Shaw, D. K., Stewart, E. T., Youker, J. E., and Metter, G. E. An evaluation of colon cleansing regimens. AJR Am.J Roentgenol. 1977;128(1):57-59. PubMed
    6. 40192. Kolts, B. E., Lyles, W. E., Achem, S. R., Burton, L., Geller, A. J., and MacMath, T. A comparison of the effectiveness and patient tolerance of oral sodium phosphate, castor oil, and standard electrolyte lavage for colonoscopy or sigmoidoscopy preparatio

    Metformin

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

  • Dizziness Additional detail

    Castor Bean

    “Orally, castor oil has been associated with syncope or dizziness in 2-20% of patients in clinical research. In a study of women taking castor seeds as a contraceptive, there were some reports of headache.”

    Castor Bean · Natural Medicines adverse-effect record, reported in cluster headache.

    5 sources cited
    1. 40188. Present, A. J., Jansson, B., Burhenne, H. J., Dodd, G. D., Goldberg, H. I., Goldstein, H. M., Miller, R. E., Nelson, J. A., and Stewart, E. T. Evaluation of 12 colon-cleansing regimens with single-contrast barium enema. AJR Am.J Roentgenol. 1982;139(5):8 PubMed
    2. 40163. Chen, C. C., Ng, W. W., Chang, F. Y., and Lee, S. D. Magnesium citrate-bisacodyl regimen proves better than castor oil for colonoscopic preparation. J.Gastroenterol.Hepatol. 1999;14(12):1219-1222. PubMed
    3. 40187. Dodds, W. J., Scanlon, G. T., Shaw, D. K., Stewart, E. T., Youker, J. E., and Metter, G. E. An evaluation of colon cleansing regimens. AJR Am.J Roentgenol. 1977;128(1):57-59. PubMed
    4. 40192. Kolts, B. E., Lyles, W. E., Achem, S. R., Burton, L., Geller, A. J., and MacMath, T. A comparison of the effectiveness and patient tolerance of oral sodium phosphate, castor oil, and standard electrolyte lavage for colonoscopy or sigmoidoscopy preparatio
    5. 7128. Isichei CO, Das SC, Ogunkeye OO, et al. Preliminary clinical investigation of the contraceptive efficacy and chemical pathological effects of RICOM-1013-J of Ricinus communis var minor on women volunteers. Phytother Res 2000;14:40-2.

    Metformin

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

  • A skin rash Additional detail

    Castor Bean

    “Exposure to castor beans, plants, or seed dust can cause contact dermatitis and anaphylaxis in sensitive individuals. Castor oil does not appear to cause these effects. In one case report, a child developed cheilitis over the course of 3 weeks, which was determined to be an allergic reaction to castor oil contained in lip balm. Orally, castor oil did not cause rash in clinical research.”

    Castor Bean · Natural Medicines adverse-effect record, reported in dermatitis.

    3 sources cited
    1. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    2. 103864. Sánchez-Herrero A, Mateos-Mayo A, Rodríguez-Lomba E, et al. Allergic contact cheilitis in an adolescent to Ricinus communis seed oil (castor oil) in a lip balm. Contact Dermatitis. 2018;79(3):176-178.
    3. 40185. Strates, B. S. and Hofmann, L. M. A randomized study of two preparations for large bowel radiology. Pharmatherapeutica 1987;5(1):57-61.

    “Topically, the castor plant, crushed castor seeds, or castor seed dust can cause dermatitis in some patients. Castor oil does not appear to cause these effects. In one case report, a child developed cheilitis over the course of 3 weeks, which was determined to be an allergic reaction to castor oil contained in lip balm.”

    Castor Bean · Natural Medicines adverse-effect record, reported in dermatitis.

    2 sources cited
    1. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    2. 103864. Sánchez-Herrero A, Mateos-Mayo A, Rodríguez-Lomba E, et al. Allergic contact cheilitis in an adolescent to Ricinus communis seed oil (castor oil) in a lip balm. Contact Dermatitis. 2018;79(3):176-178.

    Metformin

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

  • Headache Additional detail

    Castor Bean

    “Intravenously, castor bean extract can cause multi-organ failure and death. In one case report, a 26-year-old male presented to the emergency room with severe abdominal cramps, nausea, and headache after intravenously injecting castor bean extract as a suicide attempt.”

    Castor Bean · Natural Medicines adverse-effect record, reported in cluster headache.

    6 sources cited
    1. 100835. Verougstraete N, Helsloot D, Deprez C, Heylen O, Casier I, Croes K. Lethal Injection of a Castor Bean Extract: Ricinine Quantification as a Marker for Ricin Exposure Using a Validated LC-MS/MS Method. J Anal Toxicol. 2019;43(3):e1-e5. PubMed
    2. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    3. 5612. Palatnick W, Tenenbein M. Hepatotoxicity from castor bean ingestion in a child. J Toxicol Clin Toxicol 2000;38:67-9. PubMed
    4. 92998. Ferguson TS. Castor bean ingestion and ricin toxicity in a case of attempted suicide. West Indian Med J 2011;60(5):596.
    5. 93000. Kamath JV, Rana AC, Chowdhury AR. Pro-healing effect of Cinnamomum zeylanicum bark. Phytother Res 2003;17(8):970-2.
    6. 93505. Thornton SL, Darracq M, Lo J, et al. Castor bean seed ingestions: a state-wide poison control system's experience. Clin Toxicol (Phila) 2014;52(4):265-8. PubMed

    Metformin

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

  • Nausea Additional detail

    Castor Bean

    Recorded for Castor Bean in the same Natural Medicines adverse-effect record shown under Stomach upset / Diarrhea / Vomiting above.

    Metformin

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

Reported for Castor Bean but not commonly for Metformin: bleeding in the gut, an electrolyte imbalance, an allergic reaction and stomach pain.

Effects for Metformin come from the ADVERSE REACTIONS section of its FDA label; effects for Castor Bean 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.

Special populations

Castor Bean in Pregnancy & Breastfeeding

Pregnancy Possibly Safe

When castor oil is used orally in pregnant women at term. Although there have been reports of fetal meconium passage being more common with castor oil use in pregnant women, clinical research shows that the incidence of fetal meconium passage does not significantly differ from no castor oil use. Midwives routinely use castor oil for labor induction in pregnant women at term. This practice does not appear to adversely affect the mother or fetus. However, castor oil should not be used without the supervision of a clinician.

Pregnancy Likely Unsafe

When castor oil is used orally in pregnant women who are not at term. Castor oil might induce premature labor and induce miscarriage; avoid using.

Pregnancy Unsafe

When the whole seed is used orally. The chewed or uncoated seeds can cause severe toxic effects, including death; avoid using. There is insufficient reliable information available about the safety of using the hulled seed or topical use of castor during pregnancy.

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

From our Q&A

Questions About Castor Bean or Metformin

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

This page covers Castor Bean only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin page lists 258 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 217 moderate · 39 minor.

From our pharmacist’s overview on the Metformin page

“Siberian cocklebur is the ingredient I most want anyone taking metformin (Glucophage) to know about. It has caused severe low blood sugar in people, documented in humans, and it should not be combined with any glucose-lowering medication.”

Reviewed by 2 · Jul 18, 2026

Open the Metformin interaction page

How much people look this up

Where Castor Bean and Metformin 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 Castor Bean
Steady interest

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

29 days ago today
Medication Metformin
Top 1%

#29 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 Castor Bean reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Castor Bean and Metformin 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 Castor Bean

What is Castor Bean?

  • Constipation relief
  • Skin and hair care
  • Labor induction (folk use)
  • Topical anti-inflammatory packs
  • Joint and muscle massage

Castor bean is the source of castor oil, a well-known stimulant laxative, but the raw seeds contain ricin, a potent and potentially deadly poison. The processed oil is generally considered safe when used as directed, while the whole or chewed seeds should never be eaten. Always talk to a pharmacist or doctor before using castor oil, especially during pregnancy or for children.

Ricinus communis · Euphorbiaceae · Seeds (beans) and the oil pressed from them · Castor oil (liquid), capsules, topical oils, and packs

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

Castor Bean: dosing

There is no single standard dose for all uses. For constipation, castor oil is sold as an over-the-counter laxative, and you should follow the directions on the product label or your pharmacist's advice. It is meant for short-term, occasional use only.Do not use higher amounts hoping for a stronger effect, and do not use it daily without medical guidance.

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

Read the full Castor Bean monograph & all interactions
Medication

About Metformin

What Is Metformin Used For?

Brand names: Glucophage, Metformin

Metformin is used to improve blood sugar (glucose) control in people with type 2 diabetes mellitus. It is always used together with diet and exercise, not instead of them.

Metformin hydrochloride tablets and oral solution are approved for adults and children 10 years and older. Metformin hydrochloride extended-release tablets — including brands such as Fortamet, Glumetza, and Metformin Hydrochloride Extended Release — are approved for adults only.

See full Metformin drug information
Keep checking

Other Drugs & Castor Bean

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

0Major
75Moderate
0Minor
2,754No known interaction
75 Moderate 2,754 No interaction
Moderate

75 interactions

Showing 60 of 75 moderate interactions — see all 75 on the Castor Bean page.

No interaction 2,754 drugs checked — show the list

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

Showing the 60 most looked-up of 2,754 medications checked with no known interaction — see the full Castor Bean list.

See the full Castor Bean interactions page
See every supplement checked against Metformin, ranked by severity
Evidence & sources

Castor Bean References

The 25 references that drive our Castor Bean 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. 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. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  3. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
  4. McFarlin BL, Gibson MH, O'Rear J, Harman P. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J Nurse Midwifery 1999;44:205-16. PubMed
  5. Steingrub JS, Lopez T, Teres D, et al. Amniotic fluid embolism associated with castor oil ingestion. Crit Care Med 1988;16:642-3. PubMed
  6. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
  7. Palatnick W, Tenenbein M. Hepatotoxicity from castor bean ingestion in a child. J Toxicol Clin Toxicol 2000;38:67-9. PubMed
  8. Isichei CO, Das SC, Ogunkeye OO, et al. Preliminary clinical investigation of the contraceptive efficacy and chemical pathological effects of RICOM-1013-J of Ricinus communis var minor on women volunteers. Phytother Res 2000;14:40-2.
  9. Garry D, Figueroa R, Guillaume J, Cucco V. Use of castor oil in pregnancies at term. Altern Ther Health Med 2000;6:77-9.
  10. Audi J, Belson M, Patel M, et al. Ricin poisoning: a comprehensive review. JAMA 2005;294:2342-51.
  11. Chen, C. C., Ng, W. W., Chang, F. Y., and Lee, S. D. Magnesium citrate-bisacodyl regimen proves better than castor oil for colonoscopic preparation. J.Gastroenterol.Hepatol. 1999;14(12):1219-1222. PubMed
  12. Azhari, S., Pirdadeh, S., Lotfalizadeh, M., and Shakeri, M. T. Evaluation of the effect of castor oil on initiating labor in term pregnancy. Saudi.Med J 2006;27(7):1011-1014. DOI
  13. Kris, M. G., Gralla, R. J., Clark, R. A., Tyson, L. B., and Groshen, S. Control of chemotherapy-induced diarrhea with the synthetic enkephalin BW942C: a randomized trial with placebo in patients receiving cisplatin. J Clin.Oncol. 1988;6(4):663-668. PubMed
  14. Mitri, F., Hofmeyr, G. J., and van Gelderen, C. J. Meconium during labour--self-medication and other associations. S.Afr.Med J 4-4-1987;71(7):431-433.
  15. Strates, B. S. and Hofmann, L. M. A randomized study of two preparations for large bowel radiology. Pharmatherapeutica 1987;5(1):57-61.

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 Castor Bean and Metformin Together: Common Questions

Is it safe to take Castor Bean with Metformin?
We do not list a known interaction between Castor Bean and Metformin. 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 Castor Bean and Metformin have any of the same side effects?
Yes — our sources link each of them separately to 8 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 Castor Bean and Metformin combination checked?
Interactions in our licensed database are recorded against drug classes. Metformin is filed under 5 classifications, and Castor Bean has documented interactions with 1 drug class — none of Metformin'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 Castor Bean interact with any other medications?
Yes. Castor Bean has 75 documented drug interactions in our database — Metformin 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 Metformin interact with any supplements?
Yes. Metformin has documented interactions with 258 supplements in our database — Castor Bean is not one of them. The Metformin 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

Castor Bean monograph Uses, safety profile, and every drug interaction in one place Metformin drug information The full plain-English guide to this medication Metformin supplement interactions Every supplement checked against Metformin, 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 25 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metformin and Castor Bean?

Our pharmacists answer your medication & supplement questions — free.

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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.