Drug & supplement interaction

Gras + Pembrolizumab

Pembrolizumab brand name: Keytruda.

No Known Interaction
Medically reviewed by · Updated June 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Gras and Pembrolizumab 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.

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Interaction report

Gras and Pembrolizumab

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 Pembrolizumab and Gras 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 Gras at all — not against Pembrolizumab, 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.

Gras safety at a glance

Gras overall Not established We cannot confirm what "Gras" is, so its safety is unknown.
Pregnancy Avoid Because the product is unidentified, avoid it during pregnancy unless a doctor confirms it is safe.
Breastfeeding Avoid With no reliable information, avoid it while breastfeeding unless cleared by your doctor.

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

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

What Pembrolizumab’s Own FDA Label Lists

This is not an interaction — none of it involves Gras. These are the most notable effects listed in the ADVERSE REACTIONS section of Pembrolizumab’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you take both. 10 of them are worth acting on rather than waiting out — marked below.

  • Low magnesium Worth acting on
  • A change in thyroid levels Worth acting on
  • Trouble swallowing Worth acting on
  • High potassium Worth acting on
  • Low sodium Worth acting on
  • Low potassium Worth acting on
  • A heart attack Worth acting on
  • Blood clots Worth acting on
  • Heart failure Worth acting on
  • High blood sugar Worth acting on

Showing the 10 most notable of 57 label-listed effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

From the ADVERSE REACTIONS section of the FDA label for Pembrolizumab. Read the label on DailyMed › Where a percentage is shown, it is the share of 100,432 voluntary FDA FAERS reports for Pembrolizumab that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Gras’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Gras side to compare — that is a limit of the record, not a statement that Gras has no side effects.

Everything else you take

See Every Supplement That Interacts With Pembrolizumab

This page covers Gras only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Pembrolizumab page lists 1 supplement it has a documented interaction with, worst first, each one explained.

The most serious there right now: American Pawpaw (minor).

By severity: 1 minor.

From our pharmacist’s overview on the Pembrolizumab page

“For a drug used against so many different cancers, pembrolizumab (Keytruda) has a remarkably short supplement file. Just one ingredient appears on it, American pawpaw, and even that lone entry is rated minor and judged unlikely to cause real trouble.”

Reviewed by 2 · Jul 18, 2026

Open the Pembrolizumab interaction page

How much people look this up

Where Gras and Pembrolizumab 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 Gras
Steady interest

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

29 days ago today
Medication Pembrolizumab
Top half

#886 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. Gras is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Gras reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Gras and Pembrolizumab records this page draws on were last updated June 20, 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 Gras

What is Gras?

We could not find reliable information about a dietary supplement or herb called "Gras." The name may be a misspelling, a brand name, or a local/regional term, so we cannot confirm what it is, what it does, or whether it is safe. Please double-check the name with your pharmacist or the product label before using it.

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

Gras: dosing

There is no established or recommended dose for "Gras" because the product cannot be reliably identified. We will not guess an amount. If you have a labeled product, follow the manufacturer's instructions only after confirming the actual ingredient with a pharmacist or doctor.

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

Read the full Gras monograph & all interactions
Medication

About Pembrolizumab Injection

What Is Pembrolizumab Injection Used For?

Brand name: Keytruda

Pembrolizumab is used to treat a wide range of cancers — including melanoma (skin cancer), lung cancer, head and neck cancers, bladder cancer, certain colorectal cancers, cervical cancer, kidney cancer, liver cancer, and many others. It can be used alone or combined with chemotherapy, depending on the cancer type and stage.

For some cancers, it's given before surgery (neoadjuvant), after surgery (adjuvant), or both — to help shrink tumors or reduce the chance the cancer comes back. Some uses require a lab test to confirm your tumor has certain markers (like PD-L1 expression) before starting treatment.

Most-Reported Side Effects for Pembrolizumab

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Malignant neoplasm progression 12,012 reports
Diarrhea 5,719 reports
Fatigue 5,113 reports
Fever 3,870 reports
Rash 3,719 reports
See full Pembrolizumab Injection drug information
Keep checking

Other Drugs & Gras

Browse every other medication we’ve checked against Gras — 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 Gras 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 Gras list.

See the full Gras interactions page
See every supplement checked against Pembrolizumab, ranked by severity
Evidence & sources

Gras References

The 3 sources that drive our Gras monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Gras is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.

  1. Dietary and Herbal Supplements — NIH NCCIH Source
  2. Herbs and Supplements — MedlinePlus Source
  3. Generally Recognized as Safe (GRAS) — U.S. Food and Drug Administration Source

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 Gras and Pembrolizumab Together: Common Questions

Is it safe to take Gras with Pembrolizumab?
We do not list a known interaction between Gras and Pembrolizumab. 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.
Does Pembrolizumab interact with any supplements?
Yes. Pembrolizumab has documented interactions with 1 supplement in our database — Gras is not one of them. The Pembrolizumab 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

Gras monograph Uses, safety profile, and every drug interaction in one place Pembrolizumab Injection drug information The full plain-English guide to this medication Pembrolizumab supplement interactions Every supplement checked against Pembrolizumab, 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 Pembrolizumab and Gras?

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.