Vitamin B12 + Pembrolizumab
Pembrolizumab brand name: Keytruda.
We found no known interaction between Vitamin B12 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. 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.
Vitamin B12 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 Vitamin B12 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.
Vitamin B12 safety at a glance
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.
Why No Interaction Is Listed for Pembrolizumab
Interactions in our licensed database are recorded against drug classes, not just single drug names. Pembrolizumab is filed under a single classification — antineoplastics. Vitamin B12 has documented interactions with 1 drug class — the most serious being metformin (glucophage) (minor) — and none of Pembrolizumab’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.
Vitamin B12 Does Interact With Other Medications
Vitamin B12 has 20 minor known drug interactions in our database — Pembrolizumab isn’t one of them. If you take anything else, check it against the full list below.
Check Another of Your Medications Against Vitamin B12
We haven’t checked that one against Vitamin B12 yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Vitamin B12. Pick one to open its full report.
Vitamin B12 in Pregnancy & Breastfeeding
When used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA for vitamin B12 during pregnancy is 2.6 mcg daily. There is insufficient reliable information available about the safety of larger amounts of vitamin B12 during pregnancy.
When used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA of vitamin B12 during lactation is 2.8 mcg daily. There is insufficient reliable information available about the safety of larger amounts of vitamin B12 while breastfeeding.
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
What Pembrolizumab Is Prescribed For, and What Vitamin B12 Has Been Studied For
These two come up together because they touch the same health topic — not because they do the same job. Pembrolizumab is a prescription medicine with approved uses on its FDA label. Vitamin B12 is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.
Pembrolizumab is prescribed for: 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.
Vitamin B12 has been studied for:
-
Cervical cancer studied, not established Vitamin B12 has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows
Vitamin B12 for cervical cancer
It is unclear if oral vitamin B12 reduces cervical cancer risk.
Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Pembrolizumab on your own; if you are taking Vitamin B12 for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.
Questions About Vitamin B12 or Pembrolizumab
These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Vitamin B12 or Pembrolizumab, 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.
See Every Supplement That Interacts With Pembrolizumab
This page covers Vitamin B12 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
Taking Vitamin B12 as Part of a Dietary Supplement Product? Check It for Interactions
We hold 26,496 real supplement products containing Vitamin B12, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin B12. Even though Vitamin B12 itself has no known interaction with Pembrolizumab, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:
Where Vitamin B12 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.
#7 of 1,452 supplements looked up here in the last 7 days
#143 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.
- Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Vitamin B12 reference on this page ↓
- Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Vitamin B12 and Pembrolizumab 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.
About Vitamin B12
What is Vitamin B12?
- Treating or preventing B12 deficiency
- Pernicious anemia
- Low energy and fatigue
- Nerve health and tingling/numbness
- Support for vegetarians and vegans
Vitamin B12 (cobalamin) is an essential nutrient your body needs to make red blood cells, keep nerves healthy, and support DNA. Supplements are very helpful for people who are deficient — such as vegans, older adults, and those with absorption problems — but taking extra B12 when you are not deficient is unlikely to boost energy or health. Talk to your pharmacist or doctor if you think you may be low.
Not applicable (a vitamin, not a plant part) · Tablets, capsules, sublingual (under-the-tongue) tablets, lozenges, liquid drops, nasal spray, and injections
An interaction check asks whether these two react with each other — it does not ask whether Vitamin B12 is a good idea for someone in your situation. Here is what our Vitamin B12 record says about it on its own.
Vitamin B12: dosing
The right amount of B12 depends on your age, diet, health, and whether you are deficient. Many daily supplements and multivitamins contain amounts well above the basic daily requirement, which is safe because excess is removed by the body.People who are deficient or who absorb B12 poorly sometimes need much higher doses or injections, which should be guided by a healthcare provider.
From our Vitamin B12 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 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.
Other Drugs & Vitamin B12
Browse every other medication we’ve checked against Vitamin B12 — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
20 interactions
- Metformin ›
- Metformin Hydrochloride ›
- Metformin, Sitagliptin ›
- Alogliptin, Metformin ›
- Canagliflozin, Metformin ›
- Canagliflozin, Metformin Hydrochloride ›
- Dapagliflozin Propanediol, Metformin ›
- Dapagliflozin, Metformin Hydrochloride, Saxagliptin Hydrochloride ›
- Empagliflozin, Linagliptin, Metformin Hydrochloride ›
- Empagliflozin, Metformin ›
- Empagliflozin, Metformin Hydrochloride ›
- Ertugliflozin, Metformin Hydrochloride ›
- Glipizide, Metformin ›
- Glyburide, Metformin ›
- Linagliptin, Metformin Hydrochloride ›
- Metformin, Linagliptin ›
- Metformin, Rosiglitazone ›
- Pioglitazone, Metformin ›
- Saxagliptin, Metformin Xr ›
- Sitagliptin, Metformin ›
No interaction 2,809 drugs checked — show the list
We also checked Vitamin B12 against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Sertraline ›
- Testosterone ›
- Losartan Potassium ›
- Metoprolol ›
- Aspirin ›
- Ivermectin ›
- Rivaroxaban ›
- Rosuvastatin ›
- Escitalopram ›
- Tadalafil ›
- Acetaminophen ›
- Clopidogrel ›
- Valacyclovir ›
- Atorvastatin ›
- Docusate ›
- Hydroxyurea ›
- Abemaciclib ›
- Methamphetamine ›
- Ibuprofen ›
- Sumatriptan ›
- Semaglutide ›
- Tirzepatide ›
- Warfarin Sodium ›
- Prednisone ›
- Propranolol ›
- Lisdexamfetamine ›
- Acyclovir ›
- Bupropion ›
- Amoxicillin ›
- Lisinopril ›
- Bendamustine ›
- Amitriptyline ›
- Doxycycline ›
- Lamotrigine ›
- Fluoxetine ›
- Methotrexate ›
- Acetaminophen, Codeine ›
- Gabapentin ›
- Amphetamine ›
- Pregabalin ›
- Isotretinoin ›
- Dextroamphetamine ›
- Azithromycin ›
- Clonazepam ›
- Quetiapine ›
- Omeprazole ›
- Amlodipine Besylate ›
- Methylene Blue ›
- Duloxetine ›
- Letrozole ›
- Buspirone ›
- Citalopram ›
- Ciprofloxacin ›
- Naproxen ›
- Bisoprolol ›
Showing the 60 most looked-up of 2,809 medications checked with no known interaction — see the full Vitamin B12 list.
Vitamin B12 References
The 30 references that drive our Vitamin B12 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.
- Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000). Washington, DC: National Academy Press, 2000. Available at: http://b
- Hartman TJ, Woodson K, Stolzenberg-Solomon R, et al. Association of the B-vitamins pyridoxal 5'-phosphate (B6), B12, and folate with lung cancer risk in older men. Am J Epidemiol 2001;153:688-94.. DOI
- Jansen T, Romiti R, Kreuter A, Altmeyer P. Rosacea fulminans triggered by high-dose vitamins B6 and B12. J Eur Acad Dermatol Venereol 2001;15:484-5..
- Lange H, Suryapranata H, De Luca G, et al. Folate therapy and in-stent restenosis after coronary stenting. N Engl J Med 2004;350:2673-81. PubMed
- Collin, S. M., Metcalfe, C., Refsum, H., Lewis, S. J., Zuccolo, L., Smith, G. D., Chen, L., Harris, R., Davis, M., Marsden, G., Johnston, C., Lane, J. A., Ebbing, M., Bonaa, K. H., Nygard, O., Ueland, P. M., Grau, M. V., Baron, J. A., Donovan, J. L., Nea
- Geissbuhler, P., Mermillod, B., and Rapin, C. H. Elevated serum vitamin B12 levels associated with CRP as a predictive factor of mortality in palliative care cancer patients: a prospective study over five years. J.Pain Symptom.Manage. 2000;20(2):93-103. PubMed
- Salles, N., Herrmann, F., Sakbani, K., Rapin, C. H., and Sieber, C. High vitamin B12 level: a strong predictor of mortality in elderly inpatients. J Am Geriatr.Soc 2005;53(5):917-918.
- Looker, H. C., Fagot-Campagna, A., Gunter, E. W., Pfeiffer, C. M., Sievers, M. L., Bennett, P. H., Nelson, R. G., Hanson, R. L., and Knowler, W. C. Homocysteine and vitamin B(12) concentrations and mortality rates in type 2 diabetes. Diabetes Metab Res R
- Uhl, W., Nolting, A., Golor, G., Rost, K. L., and Kovar, A. Safety of hydroxocobalamin in healthy volunteers in a randomized, placebo-controlled study. Clin Toxicol (Phila) 2006;44 Suppl 1:17-28. PubMed
- Borron, S. W., Baud, F. J., Barriot, P., Imbert, M., and Bismuth, C. Prospective study of hydroxocobalamin for acute cyanide poisoning in smoke inhalation. Ann Emerg.Med 2007;49(6):794-801, 801. PubMed
- Borron, S. W., Baud, F. J., Megarbane, B., and Bismuth, C. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg.Med 2007;25(5):551-558. PubMed
- Lewis, J. G. Gout, Steatorrhoea, and Megaloblastic Anaemia. Ann Rheum.Dis 1962;21(3):284-286. PubMed
- Tal, S., Shavit, Y., Stern, F., and Malnick, S. Association between vitamin B12 levels and mortality in hospitalized older adults. J Am Geriatr.Soc 2010;58(3):523-526. PubMed
- Baztan, J. J., Gavidia, J. J., Gomez-Pavon, J., Esteve, A., and Ruiperez, I. High vitamin B12 levels and in-hospital mortality. J Am Geriatr.Soc 2010;58(11):2237-2238. PubMed
- Omboni, E., Checchini, M., and Longoni, F. [Hypopotassemia and megaloblastic anemia. Presentation of a case]. Minerva Med 8-31-1987;78(16):1255-1257.
- Aalfs As, Scholvinck LH, Horvath B. Acneiform eruption in a 5-year old due to vitamin B12 supplementation. Eur J Dermatol 2013;23(5):726-7. PubMed
- Balta I, Ozuguz P. Vitamin B12-induced acneiform eruption. Cutan Ocul Toxicol 2014;33(2):94-5. PubMed
- Carman KB, Belgemen T, Yis U. Involuntary movements misdiagnosed as seizure during vitamin B12 treatment. Pediatr Emerg Care 2013;29(11):1223-4. PubMed
- Djuric V, Bogic M, Popadic AP, et al. Anaphylactic reaction to hydroxycobalamin with tolerance to cyanocobalamin. Ann Allergy Asthma Immunol 2012;108(3):207-8. PubMed
- Kartel O, Gulec M, Demirel F, et al. Vitamin B12 allergy and successful desensitization with cyanocobalamin: A case report. Allergol Immunopath (Madr) 2012;40(5):324-5.
- Patiroglu T, Unal E, Yildirim S. Infantile tremor syndrome associated with cobalamin therapy: A case report. Clin Neurol Neurosurg 2013;115(9):1903-5. PubMed
- Schulte S, Barkema LW, Kardaun SH. Long-lasting atypical acneiform eruption with prominent comedones induced by hydroxocobalamin (vitamin B12). J Dtsch Dermatol Ges 2014;12(6):502-3.
- Zanus C, Alberini E, Costa P, et al. Involuntary movements after correction of vitamin B12 deficiency: A video-case report. Epileptic Disord 2012;14(2):174-80. PubMed
- Fanidi A, Carreras-Torres R, Larose TL, et al. Is high vitamin B12 status a cause of lung cancer? Int J Cancer. 2019 Sep 15;145(6):1499-1503. PubMed
- Fujita Y, Mizukami T, Maya Y, et al. Vitamin B12 allergy manifesting as lymphomatoid contact dermatitis. Eur J Dermatol. 2020;30(3):304-305. PubMed
- Dépret F, Hoffmann C, Daoud L, et al. Association between hydroxocobalamin administration and acute kidney injury after smoke inhalation: a multicenter retrospective study. Crit Care. 2019;23(1):421. PubMed
- Khairan P, Sobue T, Eshak ES, et al. Association of dietary intakes of vitamin B12, vitamin B6, folate, and methionine with the risk of esophageal cancer: the Japan Public Health Center-based (JPHC) prospective study. BMC Cancer 2021;21(1):982. PubMed
- Evans J, Pandya A, Ding Y, Qunibi WY. Hydroxocobalamin-Induced Oxalate Nephropathy in a Patient With Smoke Inhalation. Kidney Int Rep 2021;6(8):2228-2231. PubMed
- Lacombe V, Chabrun F, Lacout C, et al. Persistent elevation of plasma vitamin B12 is strongly associated with solid cancer. Sci Rep 2021;11(1):13361. PubMed
- Pegalajar-García MD, Cebolla-Verdugo M, Prados-Carmona Á, Llamas-Segura C, Navarro-Triviño FJ. Systemic allergic dermatitis to cobalt present in cyanocobalamin supplementation. Contact Dermatitis 2023;89(3):203-205. PubMed
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 Vitamin B12 and Pembrolizumab Together: Common Questions
Is it safe to take Vitamin B12 with Pembrolizumab?
Do Vitamin B12 and Pembrolizumab have any of the same side effects?
Are Vitamin B12 and Pembrolizumab used for the same thing?
How was the Vitamin B12 and Pembrolizumab combination checked?
Does Vitamin B12 interact with any other medications?
Does Pembrolizumab interact with any supplements?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Keep Exploring
Still Have a Question About Pembrolizumab and Vitamin B12?
Our pharmacists answer your medication & supplement questions — free.
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.