Lady Fern + Pembrolizumab
Pembrolizumab brand name: Keytruda.
We found no known interaction between Lady Fern 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.
Lady Fern 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 Lady Fern 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 Lady Fern 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.
Lady Fern safety at a glance
Safety guidance is general; always confirm with your pharmacist or doctor for your situation.
See Every Supplement That Interacts With Pembrolizumab
This page covers Lady Fern 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
Where Lady Fern 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.
#1,148 of 1,452 supplements looked up here in the last 7 days
#739 of 2,830 medications looked up here in the last 7 days
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. Lady Fern 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 Lady Fern reference on this page ↓
- Freshness: we automatically re-check this combination every week — this pair was last verified September 27, 2026. The Lady Fern 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.
About Lady Fern
What is Lady Fern?
- Traditional digestive complaints
- Folk remedy for intestinal worms
- Topical use for wounds and skin irritation
- General traditional tonic
- Eaten as a foraged spring vegetable (fiddleheads)
Lady fern is a woodland fern used in some folk traditions and occasionally foraged for its young fronds (fiddleheads). There is very little scientific evidence to support any medicinal use, and some ferns can be unsafe if raw or improperly prepared, so caution is warranted.
Athyrium filix-femina · Athyriaceae · Rhizome (rootstock) and young fronds (fiddleheads) · Dried rhizome, traditional decoction, occasionally cooked young fronds (fiddleheads) as food
An interaction check asks whether these two react with each other — it does not ask whether Lady Fern is a good idea for someone in your situation. Here is what our Lady Fern record says about it on its own.
Lady Fern: dosing
There is no established or standardized medicinal dose for lady fern. It has not been studied enough to recommend a safe and effective amount for any condition.If you choose to use a product that contains lady fern, follow the directions on the label and do not exceed the suggested amount. For fiddleheads used as food, cook them fully according to trusted preparation guidance.
From our Lady Fern monograph — the full record covers uses, side effects and every documented interaction.
About Pembrolizumab Injection
What Is Pembrolizumab Injection Used For?
Brand name: Keytruda
Pembrolizumab Injection (Keytruda) is used to treat many types of cancer. Some uses are for cancer that has spread or can’t be removed by surgery. Others are given before or after surgery.
Main cancer types include melanoma, non-small cell lung cancer, mesothelioma, head and neck squamous cell cancer, classical Hodgkin lymphoma, urothelial (bladder) cancer, colorectal cancer, gastric and esophageal cancer, cervical cancer, liver cancer, biliary tract cancer, Merkel cell carcinoma, kidney cancer, endometrial cancer, cutaneous squamous cell carcinoma, triple-negative breast cancer and ovarian cancer. Many uses depend on tumor tests and are given alone or with other cancer drugs.
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.
Other Drugs & Lady Fern
Browse every other medication we’ve checked against Lady Fern — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
No interaction 2,829 drugs checked — show the list
We also checked Lady Fern against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Ivermectin ›
- Abemaciclib ›
- Testosterone ›
- Sertraline ›
- Losartan Potassium ›
- Acetaminophen ›
- Rosuvastatin ›
- Aspirin ›
- Escitalopram ›
- Metoprolol ›
- Clopidogrel ›
- Atorvastatin ›
- Rivaroxaban ›
- Isotretinoin ›
- Tirzepatide ›
- Warfarin Sodium ›
- Ibuprofen ›
- Methamphetamine ›
- Amlodipine Besylate ›
- Docusate ›
- Valacyclovir ›
- Prednisone ›
- Metformin ›
- Tadalafil ›
- Amitriptyline ›
- Sumatriptan ›
- Hydroxyurea ›
- Levothyroxine, Liothyronine ›
- Semaglutide ›
- Lisdexamfetamine ›
- Propranolol ›
- Amphetamine ›
- Methotrexate ›
- Lisinopril ›
- Amoxicillin ›
- Bupropion ›
- Fluoxetine ›
- Azithromycin ›
- Doxycycline ›
- Pregabalin ›
- Gabapentin ›
- Bendamustine ›
- Dextroamphetamine ›
- Lamotrigine ›
- Naproxen ›
- Acetaminophen, Aspirin, Caffeine ›
- Acyclovir ›
- Quetiapine ›
- Clonazepam ›
- Buspirone ›
- Omeprazole ›
- Letrozole ›
- Duloxetine ›
- Citalopram ›
- Methylene Blue ›
Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Lady Fern list.
Lady Fern References
The 2 sources that drive our Lady Fern monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Lady Fern is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.
- Herbs at a Glance — NIH National Center for Complementary and Integrative Health (NCCIH) Source
- Herbs and Supplements — MedlinePlus (U.S. National Library of Medicine) 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.
Taking Lady Fern and Pembrolizumab Together: Common Questions
Is it safe to take Lady Fern with Pembrolizumab?
Does Pembrolizumab interact with any supplements?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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Still Have a Question About Pembrolizumab and Lady Fern?
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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.