Drug & supplement interaction

Capers + Metformin Hydrochloride

Metformin Hydrochloride brand name: Riomet ER.

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

Capers has a moderate interaction with Metformin Hydrochloride. Some preliminary clinical research shows that taking caper fruit extract 1200 mg daily for 2 months can lower fasting blood glucose and glycated hemoglobin (HbA1c) in patients with type 2 diabetes who are already taking antidiabetes drugs.

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

Capers and Metformin Hydrochloride

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIDIABETES DRUGS

Why this applies to Metformin Hydrochloride

Metformin Hydrochloride falls under ANTIDIABETES DRUGS — the group Capers interacts with.

Some preliminary clinical research shows that taking caper fruit extract 1200 mg daily for 2 months can lower fasting blood glucose and glycated hemoglobin (HbA1c) in patients with type 2 diabetes who are already taking antidiabetes drugs. However, other research does not support this effect. Until more is known, monitor blood glucose levels closely. Medication dose adjustments may be necessary.
Some antidiabetes drugs include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), and others.
Severity Moderate 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: some early research suggests caper fruit extract (around 1200 mg a day) may nudge your blood sugar down a little on its own. If you're already taking metformin to manage type 2 diabetes, stacking a concentrated caper supplement on top could add to that effect and push your numbers lower than expected.

The main thing to watch for is your sugar dropping too low. With metformin alone that's uncommon, but combined effects can show up as shakiness, sweating, dizziness, headache, or feeling unusually tired. The evidence here is mixed and not very strong, and the caper amount you eat as food on a salad or pizza is far too small to matter. It's really only the concentrated extract worth a conversation. If you'd like to try it, check your blood sugar more often at first and let your doctor or pharmacist know.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Huseini HF, Hasani-Rnjbar S, Nayebi N, et al. Capparis spinosa L. (Caper) fruit extract in treatment of type 2 diabetic patients: a randomized double-blind placebo-controlled clinical trial. Complement Ther Med. 2013;21(5):447-52. PubMed
  2. Vahid H, Bonakdaran S, Khorasani ZM, et al. Effect of Capparis spinosa extract on metabolic parameters in patients with type-2 diabetes: A randomized controlled trial. Endocr Metab Immune Disord Drug Targets. 2019;19(1):100-107. 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

Capers Also Interacts With Other Medications

Capers has 85 moderate known drug interactions in our database — the Metformin Hydrochloride one above is one of them. If you take anything else, check it against the full list below.

Moderate 85 No known interaction 2,745 (incl. Metformin Hydrochloride)
Taking anything else?

Check Another of Your Medications Against Capers

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

Everything else you take

See Every Supplement That Interacts With Metformin Hydrochloride

This page covers Capers only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin Hydrochloride page lists 257 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 · 38 minor.

From our pharmacist’s overview on the Metformin Hydrochloride page

“Anyone taking metformin hydrochloride (Riomet ER) should treat this list with genuine care, because two of its 257 entries are rated major. Siberian cocklebur has caused severe hypoglycemia in people and should not be combined with metformin at all, and activated charcoal can adsorb the drug in the gut so less reaches your blood.”

Reviewed by 2 · Jul 18, 2026

Open the Metformin Hydrochloride interaction page

One more smart check

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

We hold 53 real supplement products containing Capers, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Capers. Your product may carry other ingredients that interact with Metformin Hydrochloride too, on top of Capers — 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 Capers and Metformin Hydrochloride 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 Capers
Steady interest

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

29 days ago today
Medication Metformin Hydrochloride
Top 5%

#133 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 Capers

What is Capers?

  • Digestive support
  • Antioxidant source
  • Blood sugar support
  • Anti-inflammatory
  • Skin and traditional tonic uses

Capers are the edible pickled flower buds of the Capparis spinosa shrub, used widely as food and in traditional medicine. They contain antioxidant plant compounds, but high-quality human studies on health benefits are limited, so the supplement claims remain largely unproven. As a food, capers are generally safe, but talk to your pharmacist or doctor before using concentrated extracts.

Read the full Capers monograph & all interactions
Keep checking

Other Drugs & Capers

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

0Major
85Moderate
0Minor
2,744No known interaction
85 Moderate 2,744 No interaction
Moderate

85 interactions

Showing 60 of 85 moderate interactions — see all 85 on the Capers page.

No interaction 2,744 drugs checked — show the list

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

Showing the 60 most looked-up of 2,744 medications checked with no known interaction — see the full Capers list.

See the full Capers interactions page
See every supplement checked against Metformin Hydrochloride, 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
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Pharmacist Counseling Corner

Taking Capers and Metformin Hydrochloride Together: Common Questions

Can you take Capers with Metformin Hydrochloride?
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.
How serious is the Capers and Metformin Hydrochloride 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

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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.