Drug & supplement interaction

Cobalt + Methotrexate

Methotrexate brand names: Rheumatrex, Otrexup, Rasuvo, Reditrex.

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 Cobalt and Methotrexate 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

Cobalt and Methotrexate

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 Methotrexate and Cobalt 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 Cobalt at all — not against Methotrexate, 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.

Cobalt safety at a glance

Cobalt overall Avoid Inorganic cobalt supplements have no proven benefit and can cause serious toxicity, so they are generally not recommended.
Pregnancy Avoid Cobalt supplements should be avoided during pregnancy because of toxicity concerns and a lack of safety data.
Breastfeeding Avoid Avoid cobalt supplements while breastfeeding; rely on vitamin B12 for any needed cobalt.

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

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

No Interaction Found — But Data Suggests Cobalt and Methotrexate 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. 3 of them are worth acting on rather than waiting out — marked below.

  • Loss of vision Worth acting on Additional detail

    Cobalt

    “Orally, cobalt seems to be well-tolerated when taken for up to 90 days in small amounts. Taking cobalt orally long-term or in high doses may cause cardiomyopathy, hearing loss, and vision loss. Topically, cobalt-containing products can cause allergic contact dermatitis in some patients.”

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

    6 sources cited
    1. 102066. Packer M. Cobalt cardiomyopathy: a critical reappraisal in light of a recent resurgence. Circ Heart Fail 2016;9(12). pii: e003604. PubMed
    2. 102068. Lim CA, Khan J, Chelva E, Khan R, Unsworth-Smith T. The effect of cobalt on the human eye. Doc Ophthalmol 2015;130(1):43-8. PubMed
    3. 102077. Catalani S, Rizzetti MC, Padovani A, Apostoli P. Neurotoxicity of cobalt. Hum Exp Toxicol 2012;31(5):421-37. PubMed
    4. 102070. Fowler JF Jr. Cobalt. Dermatitis 2016;27(1):3-8.
    5. 102071. Zajdel NJ, Smith WA, Taintor AR, Jacob SE, Olasz EB. Chemical tattoo treatment leading to systemic cobalt hypersensitivity. Skinmed 2017;15(3):221-2.
    6. 102072. Bregnbak D, Opstrup MS, Jellesen MS, Johansen JD, Thyssen JP. Allergic contact dermatitis caused by cobalt in leather - clinical cases. Contact Dermatitis 2017;76(6):366-8. PubMed

    “Oral, occupational, and systemic exposure to cobalt may cause adverse ocular and otic effects. While rare, reversible and irreversible vision loss, optic neuropathy and atrophy, signs of abnormal retinal functioning, hearing loss, bilateral deafness, and tinnitus have been reported in patients taking cobalt for anemia, working in industries with exposure to cobalt dust, and those with cobalt-containing prosthetic joi…”

    Cobalt · Natural Medicines adverse-effect record, reported in anemia.

    3 sources cited
    1. 102068. Lim CA, Khan J, Chelva E, Khan R, Unsworth-Smith T. The effect of cobalt on the human eye. Doc Ophthalmol 2015;130(1):43-8. PubMed
    2. 102074. Paustenbach DJ, Galbraith DA, Finley BL. Interpreting cobalt blood concentrations in hip implant patients. Clin Toxicol (Phila) 2014;52(2):98-112. PubMed
    3. 102077. Catalani S, Rizzetti MC, Padovani A, Apostoli P. Neurotoxicity of cobalt. Hum Exp Toxicol 2012;31(5):421-37. PubMed

    Methotrexate

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

  • Seizures Worth acting on Additional detail

    Cobalt

    “Exposure to cobalt may cause reversible neurologic adverse effects in some patients. Demyelinating neuropathy, cognitive decline, headaches, depression, convulsions, and forgetfulness have been reported in patients with cobalt-containing hip joint prostheses. Vertigo and impairment in memory and attention have been reported after occupational exposure to cobalt.”

    Cobalt · Natural Medicines adverse-effect record, reported in depression.

    3 sources cited
    1. 102074. Paustenbach DJ, Galbraith DA, Finley BL. Interpreting cobalt blood concentrations in hip implant patients. Clin Toxicol (Phila) 2014;52(2):98-112. PubMed
    2. 102076. Zywiel MG, Cherian JJ, Banerjee S, et al. Systemic cobalt toxicity from total hip arthroplasties: review of a rare condition Part 2. measurement, risk factors, and step-wise approach to treatment. Bone Joint J 2016;98-B(1):14-20. PubMed
    3. 102077. Catalani S, Rizzetti MC, Padovani A, Apostoli P. Neurotoxicity of cobalt. Hum Exp Toxicol 2012;31(5):421-37. PubMed

    Methotrexate

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

  • Anemia Worth acting on Additional detail

    Cobalt

    “Oral, occupational, and systemic exposure to cobalt may cause cardiomyopathy. While rare, this adverse effect has been reported in patients taking cobalt for anemia, consuming cobalt-fortified beer, working in industries with exposure to cobalt dust, and those with cobalt-containing prosthetic joints.”

    Cobalt · Natural Medicines adverse-effect record, reported in anemia.

    2 sources cited
    1. 102066. Packer M. Cobalt cardiomyopathy: a critical reappraisal in light of a recent resurgence. Circ Heart Fail 2016;9(12). pii: e003604. PubMed
    2. 102076. Zywiel MG, Cherian JJ, Banerjee S, et al. Systemic cobalt toxicity from total hip arthroplasties: review of a rare condition Part 2. measurement, risk factors, and step-wise approach to treatment. Bone Joint J 2016;98-B(1):14-20. PubMed

    Methotrexate

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

  • Ringing in the ears Additional detail

    Cobalt

    Recorded for Cobalt in the same Natural Medicines adverse-effect record shown under Loss of vision above.

    Methotrexate

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

  • Chills / Cough Additional detail

    Cobalt

    “Occupational exposure to cobalt can cause interstitial lung disease (ILD). Patients with subacute cobalt-related ILD may present with dyspnea, cough, fevers, chills, and weight loss a few months to years after exposure, and symptoms typically resolve after removal of the exposure.”

    Cobalt · Natural Medicines adverse-effect record, reported in cough.

    1 source cited
    1. 102067. Adams TN, Butt YM, Batra K, Glazer CS. Cobalt related interstitial lung disease. Respir Med 2017;129:91-7. PubMed

    Methotrexate

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

  • Dizziness / Headache Additional detail

    Cobalt

    Recorded for Cobalt in the same Natural Medicines adverse-effect record shown under Seizures above.

    Methotrexate

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

  • A skin rash Additional detail

    Cobalt

    “Topically, cobalt can cause allergic contact dermatitis. Numerous cases of allergic skin reactions have been reported after contact with cobalt in leather goods, jewelry, nail polishes, cobalt blue tattoo ink, and cement.”

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

    5 sources cited
    1. 102069. Guarneri F, Guarneri C, Cannavò SP. Nail-art and cobalt allergy. Contact Dermatitis 2010;62(5):320-1. PubMed
    2. 102070. Fowler JF Jr. Cobalt. Dermatitis 2016;27(1):3-8.
    3. 102071. Zajdel NJ, Smith WA, Taintor AR, Jacob SE, Olasz EB. Chemical tattoo treatment leading to systemic cobalt hypersensitivity. Skinmed 2017;15(3):221-2.
    4. 102072. Bregnbak D, Opstrup MS, Jellesen MS, Johansen JD, Thyssen JP. Allergic contact dermatitis caused by cobalt in leather - clinical cases. Contact Dermatitis 2017;76(6):366-8. PubMed
    5. 102073. Simonsen AB, Friis UF, Johansen JD, Zachariae C, Sloth JJ, Thyssen JP. Occupational allergic contact dermatitis caused by cobalt in machine oil. Contact Dermatitis 2019;80(1):59-61. PubMed

    Methotrexate

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

Reported for Cobalt but not commonly for Methotrexate: a change in thyroid levels, memory problems, hearing loss and weight loss.

Effects for Methotrexate come from the ADVERSE REACTIONS section of its FDA label; effects for Cobalt come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 489,806 voluntary FDA FAERS reports for Methotrexate that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

From our Q&A

Questions About Cobalt or Methotrexate

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

This page covers Cobalt only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methotrexate page lists 82 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Apple (major), Beer (major), Grapefruit (major) and Siberian Cocklebur (major).

By severity: 7 major · 60 moderate · 15 minor.

From our pharmacist’s overview on the Methotrexate page

“The liver is where methotrexate and supplements clash most. Methotrexate (Rheumatrex, Otrexup, Rasuvo), used for rheumatoid arthritis, psoriasis, and certain cancers, can strain the liver on its own, and 38 of the 82 interacting ingredients on this list add liver risk of their own, alcohol included, which makes this a list to approach…”

Reviewed by 2 · Jul 18, 2026

Open the Methotrexate interaction page

One more smart check

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

We hold 120 real supplement products containing Cobalt, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cobalt. Even though Cobalt itself has no known interaction with Methotrexate, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Cobalt and Methotrexate 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 Cobalt
Steady interest

#1,050 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Methotrexate
Top 5%

#49 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 Cobalt reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Cobalt and Methotrexate records this page draws on were last updated July 10, 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 Cobalt

What is Cobalt?

  • Anemia (historically)
  • Part of vitamin B12 nutrition
  • General 'energy' tonics (unproven)
  • Athletic or performance claims (unproven and risky)

Cobalt is a trace element that the body only needs as part of vitamin B12 (cobalamin); there is no proven reason to take inorganic cobalt supplements, and doing so can be harmful. If you need cobalt for nutrition, get it through vitamin B12 from food or a B12 supplement, not from standalone cobalt products.

Cobalt is a chemical element (a trace mineral), not a plant part · Cobalt salts, supplement tablets (rare and discouraged), and as part of vitamin B12 (cobalamin)

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

Cobalt: dosing

There is no established safe or beneficial dose of inorganic cobalt as a dietary supplement, and health professionals generally do not recommend taking it.The cobalt your body actually needs is supplied through vitamin B12. For B12, follow the dose on the product label or your doctor's advice.

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

Read the full Cobalt monograph & all interactions
Medication

About Methotrexate

What Is Methotrexate Used For?

Brand names: Rheumatrex, Otrexup, Rasuvo, Reditrex

Methotrexate treats a wide range of serious conditions. In cancer care, it is used for acute lymphoblastic leukemia, non-Hodgkin lymphoma, osteosarcoma, breast cancer, head and neck cancer, and gestational trophoblastic neoplasia (a rare tumor related to pregnancy). It is also used to prevent and treat meningeal leukemia (cancer affecting the lining of the brain and spinal cord).

Outside of cancer, methotrexate is prescribed for adults with rheumatoid arthritis (RA), children with polyarticular juvenile idiopathic arthritis (a form of childhood arthritis), and adults with severe psoriasis that hasn't responded well to other treatments.

Most-Reported Side Effects for Methotrexate

From FAERS, the FDA’s public side-effect reporting system (489,806 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Rheumatoid arthritis 42,798 reports
Arthralgia 40,830 reports
Fatigue 33,049 reports
Nausea 28,999 reports
Joint swelling 25,026 reports
See full Methotrexate drug information
Keep checking

Other Drugs & Cobalt

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

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

Cobalt References

The 11 references that drive our Cobalt 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. Packer M. Cobalt cardiomyopathy: a critical reappraisal in light of a recent resurgence. Circ Heart Fail 2016;9(12). pii: e003604. PubMed
  2. Adams TN, Butt YM, Batra K, Glazer CS. Cobalt related interstitial lung disease. Respir Med 2017;129:91-7. PubMed
  3. Lim CA, Khan J, Chelva E, Khan R, Unsworth-Smith T. The effect of cobalt on the human eye. Doc Ophthalmol 2015;130(1):43-8. PubMed
  4. Guarneri F, Guarneri C, Cannavò SP. Nail-art and cobalt allergy. Contact Dermatitis 2010;62(5):320-1. PubMed
  5. Fowler JF Jr. Cobalt. Dermatitis 2016;27(1):3-8.
  6. Zajdel NJ, Smith WA, Taintor AR, Jacob SE, Olasz EB. Chemical tattoo treatment leading to systemic cobalt hypersensitivity. Skinmed 2017;15(3):221-2.
  7. Bregnbak D, Opstrup MS, Jellesen MS, Johansen JD, Thyssen JP. Allergic contact dermatitis caused by cobalt in leather - clinical cases. Contact Dermatitis 2017;76(6):366-8. PubMed
  8. Simonsen AB, Friis UF, Johansen JD, Zachariae C, Sloth JJ, Thyssen JP. Occupational allergic contact dermatitis caused by cobalt in machine oil. Contact Dermatitis 2019;80(1):59-61. PubMed
  9. Paustenbach DJ, Galbraith DA, Finley BL. Interpreting cobalt blood concentrations in hip implant patients. Clin Toxicol (Phila) 2014;52(2):98-112. PubMed
  10. Zywiel MG, Cherian JJ, Banerjee S, et al. Systemic cobalt toxicity from total hip arthroplasties: review of a rare condition Part 2. measurement, risk factors, and step-wise approach to treatment. Bone Joint J 2016;98-B(1):14-20. PubMed
  11. Catalani S, Rizzetti MC, Padovani A, Apostoli P. Neurotoxicity of cobalt. Hum Exp Toxicol 2012;31(5):421-37. 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.

Pharmacist Counseling Corner

Taking Cobalt and Methotrexate Together: Common Questions

Is it safe to take Cobalt with Methotrexate?
We do not list a known interaction between Cobalt and Methotrexate. 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 Cobalt and Methotrexate have any of the same side effects?
Yes — our sources link each of them separately to 9 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.
Does Methotrexate interact with any supplements?
Yes. Methotrexate has documented interactions with 82 supplements in our database — Cobalt is not one of them. The Methotrexate 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

Cobalt monograph Uses, safety profile, and every drug interaction in one place Methotrexate drug information The full plain-English guide to this medication Methotrexate supplement interactions Every supplement checked against Methotrexate, 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 11 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Methotrexate and Cobalt?

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.