Methimazole
Methimazole is an antithyroid medicine used to treat hyperthyroidism (an overactive thyroid) from Graves’ disease or toxic multinodular goiter, and to control symptoms before thyroid surgery or radioactive iodine treatment.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 39 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Methimazole is the preferred antithyroid medicine for hyperthyroidism (an overactive thyroid) from Graves’ disease or toxic multinodular goiter, and it also settles symptoms before thyroid surgery or radioactive iodine. It works by blocking the thyroid from making new hormone, has been on the U.S. market since about 1950 and is available as a generic. Most people tolerate it well, and the side effects they tend to notice are a rash, itching or an upset stomach. Watch above all for fever or a sore throat, which can signal agranulocytosis (a dangerous drop in infection-fighting white blood cells) and needs reporting the same day.
Clinical pearls
- It cannot clear hormone already made, so improvement builds over weeks while TSH and free T4 blood tests guide the dose.
- Yellowing skin or eyes, poor appetite or pain in the upper right belly can signal liver trouble, so report them promptly.
- Warfarin needs closer INR (clotting) checks, and digoxin, beta blocker and theophylline doses may need lowering as thyroid levels normalize.
- If you are or could become pregnant, tell your prescriber, since it can cause first-trimester birth defects.
Patient information guide A plain-language walkthrough of Methimazole, written from its FDA label.
What Methimazole is used for
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Methimazole is used to treat an overactive thyroid in these situations:
- Methimazole tablets treat hyperthyroidism from Graves’ disease or toxic multinodular goiter when surgery or radioactive iodine is not an appropriate option.
- Methimazole tablets ease hyperthyroid symptoms in preparation for thyroidectomy or radioactive iodine therapy.
How Methimazole works
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Methimazole stops the thyroid from making new thyroid hormones, which brings down the excess hormone that causes hyperthyroidism.
It does not inactivate hormone already stored in the thyroid or in your blood. It also does not interfere with thyroid hormone medicine taken by mouth or by injection.
Methimazole dosage
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Methimazole tablets are taken by mouth, usually as 3 doses spread about 8 hours apart. Your starting amount depends on how severe your hyperthyroidism is, and it is later lowered to a maintenance level. Children’s doses are based on body weight.
Follow your prescriber’s directions and your pharmacy label.
Dosing details from the FDA-approved label
From the Methimazole prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
- Adults - mild hyperthyroidism (initial)
- Initial daily dosage is 15 mg, divided into 3 doses at 8-hour intervals
- Adults - moderately severe hyperthyroidism (initial)
- Initial daily dosage is 30 mg to 40 mg, divided into 3 doses at 8-hour intervals
- Adults - severe hyperthyroidism (initial)
- Initial daily dosage is 60 mg, divided into 3 doses at 8-hour intervals
- Adults - maintenance
- Maintenance dosage is 5 mg to 15 mg daily
- Pediatric - initial
- Initially, the daily dosage is 0.4 mg/kg of body weight divided into 3 doses and given at 8-hour intervals
- Weight-based dosing
- Pediatric - maintenance
- Maintenance dosage is approximately 1/2 of the initial dose
Read the label’s full dosing text
DOSAGE AND ADMINISTRATION Methimazole tablets are administered orally. The total daily dosage is usually given in 3 divided doses at approximately 8-hour intervals. Adults - The initial daily dosage is 15 mg for mild hyperthyroidism, 30 mg to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals. The maintenance dosage is 5 mg to 15 mg daily. Pediatric - Initially, the daily dosage is 0.4 mg/kg of body weight divided into 3 doses and given at 8-hour intervals. The maintenance dosage is approximately 1/2 of the initial dose.
Read the full Dosage and Administration section on DailyMed →
Methimazole side effects
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Most side effects are mild and include:
Common side effects
- Skin rash or hives
- Itching
- Nausea or vomiting
- Upset stomach
- Joint or muscle aches
- Headache
- Hair loss
- Loss of taste
- Headache, drowsiness, or dizziness (vertigo)
- Tingling or numbness
- Swelling
When to get medical help
- Fever or sore throat: call your doctor right away, as these can be signs of agranulocytosis, a dangerously low white blood cell count.
- Loss of appetite, itching, pain in the upper right belly, or yellowing of skin or eyes: these can signal liver problems.
- Signs of vasculitis (blood vessel inflammation), such as unusual skin changes, kidney problems, coughing up blood, or nerve problems: contact your doctor promptly.
- Unusual bleeding or bruising, or signs of other blood count problems: get medical advice.
- Symptoms of low blood sugar, which can occur with insulin autoimmune syndrome: seek help.
- Severe stomach pain, which may be a sign of pancreatitis: seek medical care.
Less common but serious reactions include low blood counts, liver problems, vasculitis, pancreatitis, and a lupus-like syndrome. Call your doctor right away for fever, sore throat, yellow skin or eyes, or unusual symptoms.
Methimazole warnings and precautions
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- Agranulocytosis: a potentially life-threatening drop in white blood cells. Report fever or sore throat immediately.
- Other blood problems: low platelets and aplastic anemia can occur. The drug should be stopped if these happen.
- Liver toxicity: including acute liver failure, though risk appears lower than with propylthiouracil. Watch for loss of appetite, itching, or upper right belly pain.
- Hypothyroidism: TSH and free T4 are checked routinely to adjust your dose.
- Vasculitis: can affect skin, kidneys, lungs, and nerves, and may require stopping the drug.
- Pregnancy: can cause birth defects in the first trimester and fetal goiter and cretinism.
Methimazole interactions
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Methimazole can affect how other medicines work, especially as your thyroid levels return to normal.
- Warfarin and oral blood thinners: effect may increase, so INR may need monitoring.
- Beta blockers: doses may need to be reduced as you become euthyroid.
- Digoxin and similar drugs: blood levels may rise, so a lower dose may be needed.
- Theophylline: it may clear more slowly, so a lower dose may be needed.
Interactions listed in the FDA-approved label
From the Methimazole prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
- Anticoagulants (oral), e.g., warfarin: Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants may be increased. Additional monitoring of PT/INR should be considered, especially before surgical procedures.
- β-adrenergic blocking agents: Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid.
- Digitalis glycosides: Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid. A reduced dosage of digitalis glycosides may be needed.
- Theophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid. A reduced dose of theophylline may be needed.
Read the label’s full interactions text
Drug Interactions Anticoagulants (oral) - Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. β-adrenergic blocking agents - Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid. Digitalis glycosides - Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid; a reduced dosage of digitalis glycosides may be needed. Theophylline - Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Methimazole
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- Do not use if allergic to methimazole or any ingredient in the tablets.
- Tell your prescriber if you are pregnant or planning pregnancy, because of the risk of birth defects.
- Mention any liver problems.
- Share a full list of your medicines, especially blood thinners, beta blockers, digoxin, and theophylline.
- Plan on regular blood tests to check your thyroid levels.
Methimazole overdose
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Too much methimazole can cause nausea, vomiting, stomach upset, headache, fever, joint pain, itching, and swelling. Serious blood problems such as agranulocytosis or aplastic anemia can show up within hours to days. Less often, liver, kidney, skin, or nerve problems occur. Contact your Regional Poison Control Center or seek medical care right away.
What Methimazole does in the body
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Methimazole lowers thyroid hormone production, which treats hyperthyroidism. It does not inactivate thyroid hormone that is already made, stored, or circulating, so its full effect takes time to appear.
How your body processes Methimazole
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Methimazole is readily absorbed from the digestive tract. It is broken down in the liver and removed from the body in the urine.
How to store Methimazole
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Store at 20° to 25°C (68° to 77°F) . Dispense in a tight, light-resistant container.
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Supplements & herbs that interact with Methimazole
91 supplements and herbal products have documented interactions with Methimazole in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 4
- Moderate · 77
- Minor · 10
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Nutrient depletion considerations
Methimazole has been associated with lower levels of 7 nutrients in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.
- Higher significance · 6
- Moderate · 1
Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.
Methimazole: pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Methimazole — the kind of thing our pharmacy team would talk through with you at the counter.
What is methimazole used for?
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How do I take it?
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What side effects are common?
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When should I call my doctor right away?
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Can I take it with my other medicines?
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Is it safe in pregnancy?
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Is Methimazole available over the counter?
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When was Methimazole first available?
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Who makes Methimazole?
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Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Methimazole on HelloPharmacist
Methimazole forms and strengths (how it comes)
Methimazole is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Tablet
How this form is used
- Methimazole tablets treat hyperthyroidism in Graves’ disease or toxic multinodular goiter when surgery or radioactive iodine is not appropriate.
- Methimazole tablets ease hyperthyroid symptoms before thyroidectomy or radioactive iodine therapy.
- Methimazole tablets are taken by mouth.
- Methimazole tablets are usually taken as 3 divided doses about 8 hours apart.
Methimazole on the U.S. market: products, makers and brands
How Methimazole appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
21 companies list 54 Methimazole product records with the FDA, mostly as tablet; the earliest marketing or approval year on record is 1950. Brand names on the directory include Tapazole, Felanorm, Reguzol and 1 more; the rest are generics.
Also listed with the FDA, not a patient dose form: Powder (7) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
How widely Methimazole is used (Medicaid data)
A general measure of how commonly Methimazole is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Methimazole is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Methimazole prescribed? Of the 1,601 medications we measure, Methimazole ranks #292 by Medicaid prescriptions — more than 82% of them.
Utilization by Methimazole product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
methimazole 5 MG Oral Tablet Most dispensed
Summed across the 9 of 72 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 197942
methimazole 10 MG Oral Tablet
Summed across the 8 of 63 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 197941
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Methimazole, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 17 of 135 listed Methimazole NDCs with Medicaid activity.
Compare Methimazole products
A representative set of FDA-listed product records for Methimazole — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Tablet | ||||
| 5 mg | Oral | A-S Medication Solutions | ANDA | View NDC → |
| 5 mg | Oral | AiPing Pharmaceutical, Inc. | ANDA | View NDC → |
| 10 mg | Oral | AiPing Pharmaceutical, Inc. | ANDA | View NDC → |
| 5 mg | Oral | American Health Packaging | ANDA | View NDC → |
| 10 mg | Oral | American Health Packaging | ANDA | View NDC → |
| 5 mg | Oral | AvKARE | ANDA | View NDC → |
| 10 mg | Oral | AvKARE | ANDA | View NDC → |
| 5 mg | Oral | AvPAK | ANDA | View NDC → |
| 10 mg | Oral | AvPAK | ANDA | View NDC → |
| 5 mg | Oral | Bionpharma Inc. | ANDA | View NDC → |
| 10 mg | Oral | Bionpharma Inc. | ANDA | View NDC → |
| 5 mg | Oral | Bryant Ranch Prepack × 6 listings | ANDA | View NDC → |
| 10 mg | Oral | Bryant Ranch Prepack × 7 listings | ANDA | View NDC → |
| 5 mg | Oral | Chartwell RX, LLC | ANDA | View NDC → |
| 10 mg | Oral | Chartwell RX, LLC | ANDA | View NDC → |
| 5 mg | Oral | Coupler LLC | ANDA | View NDC → |
| 10 mg | Oral | Coupler LLC | ANDA | View NDC → |
| 5 mg | Oral | Golden State Medical Supply, Inc. | ANDA | View NDC → |
| 10 mg | Oral | Golden State Medical Supply, Inc. | ANDA | View NDC → |
| 5 mg | Oral | Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc. | ANDA | View NDC → |
| 10 mg | Oral | Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc. | ANDA | View NDC → |
| 5 mg | Oral | Macleods Pharmaceuticals Limited | ANDA | View NDC → |
| 10 mg | Oral | Macleods Pharmaceuticals Limited | ANDA | View NDC → |
| 5 mg | Oral | Northstar Rx Llc | ANDA | View NDC → |
| 10 mg | Oral | Northstar Rx Llc | ANDA | View NDC → |
| 5 mg | Oral | Preferred Pharmaceuticals Inc. × 2 listings | ANDA | View NDC → |
| 10 mg | Oral | Preferred Pharmaceuticals Inc. × 2 listings | ANDA | View NDC → |
| 10 mg | Oral | Proficient Rx LP | ANDA | View NDC → |
| 5 mg | Oral | Remedyrepack Inc. × 2 listings | ANDA | View NDC → |
| 10 mg | Oral | Remedyrepack Inc. | ANDA | View NDC → |
| 5 mg | Oral | Rising Pharma Holdings, Inc. | ANDA | View NDC → |
| 10 mg | Oral | Rising Pharma Holdings, Inc. | ANDA | View NDC → |
| 5 mg | Oral | Square Pharmaceuticals Plc. | ANDA | View NDC → |
| 10 mg | Oral | Square Pharmaceuticals Plc. | ANDA | View NDC → |
| 5 mg | Oral | Strides Pharma Science Limited | ANDA | View NDC → |
| 10 mg | Oral | Strides Pharma Science Limited | ANDA | View NDC → |
| 5 mg | Oral | Upsher-Smith Laboratories, LLC | ANDA | View NDC → |
| 10 mg | Oral | Upsher-Smith Laboratories, LLC | ANDA | View NDC → |
| 5 mg | Oral | Viona Pharmaceuticals Inc. | ANDA | View NDC → |
| 10 mg | Oral | Viona Pharmaceuticals Inc. | ANDA | View NDC → |
Showing 54 of 54 products — FDA National Drug Code Directory. See every product, package size and price: browse all 54 Methimazole NDCs →
Methimazole side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Methimazole — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Methimazole in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Methimazole FDA approval history
How Methimazole went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Methimazole recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Methimazole recalls since July 2021.
✅No Methimazole recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 6835 2 dose forms · 7 strengths
-
Dose form (SCDF) Oral Solution RxCUI 2687698No current FDA listingClinical drug / strength (SCD) 5 MG/MLRxCUI 2687699 -
Dose form (SCDF) Oral Tablet RxCUI 372827In current FDA listings
Look up RxCUI 6835 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
Methimazole supply and shortage status
Whether Methimazole is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
💵 What Methimazole costs pharmacies (NADAC benchmark)
The national average invoice price pharmacies pay for the drug itself, from CMS's NADAC survey (data as of Sep 30, 2026). This is a supply-cost benchmark — not a retail price and not what you'd pay at the counter.
| Form | Strength | Pharmacy acquisition benchmark | |
|---|---|---|---|
| Tablet · Oral | 10 mg | $0.117 per tablet | NDC details & price history |
| Tablet · Oral | 5 mg | $0.070 per tablet | NDC details & price history |
Source: CMS National Average Drug Acquisition Cost (NADAC), a survey of retail pharmacy invoice prices. Benchmarks shown are the range across package sizes of a representative product for each form and strength — other manufacturers' products may differ.
Methimazole brand names
Methimazole is sold under 4 brand names in the FDA directory — Tapazole, Felanorm, Reguzol, Felimazole. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Who makes Methimazole: manufacturers and labelers
21 companies list Methimazole products with the FDA. By number of product records, the largest are Bryant Ranch Prepack, Preferred Pharmaceuticals Inc., Remedyrepack Inc.. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.
Methimazole drug class (RxNorm)
Methimazole belongs to the Thyroid Hormone Synthesis Inhibitor class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Methimazole page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. American Health Packaging is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →