Prescription medication · Thyroid Hormone (T3)
liothyronine
Also sold as Cytomel. This medicine treats hypothyroidism, a condition where your thyroid gland doesn't make enough thyroid hormone.
Data updated 2026-05-15
- 8,408
- FDA reportsLightly reported
- 17
- InteractionsSeveral interactions
- 47% less
- Generic vs brandReal savings
- $0.51
- Brand price (NADAC)
What the data shows
liothyronine (Cytomel) is a prescription Thyroid Hormone (T3), reported less often than most tracked drugs (8,408 FDA reports), with a lower-cost generic available (47% less than brand).
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
liothyronine (Cytomel) is a prescription Thyroid Hormone (T3). This medicine treats hypothyroidism, a condition where your thyroid gland doesn't make enough thyroid hormone.
Liothyronine (Cytomel) is a medicine that replaces a thyroid hormone called T3. It helps your body work properly if you don't make enough thyroid hormone on your own.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Brand Price
$0.51/unit
Generic Price
$0.27/unit
Generic Savings
47%
Generic Available
Yes (7 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine treats hypothyroidism, a condition where your thyroid gland doesn't make enough thyroid hormone.
Common side effects
Fatigue, Increased appetite, Weight loss
Key warnings
This medicine should not be used for weight loss or to treat obesity.
The sections below are summarized in plain English from liothyronine's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Liothyronine is a synthetic form of the T3 thyroid hormone. It works by increasing thyroid hormone levels in your body. This helps to regulate your body's metabolism and energy levels.
How to Take It
Take this medicine by mouth once a day. Your doctor will decide the right dose for you based on your condition and how you respond to the medicine. When switching from another thyroid medicine, your doctor will start you on a low dose of liothyronine and slowly increase it.
This is a plain-language summary of liothyronine's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant. Your dose of liothyronine may need to be adjusted during pregnancy. This medicine passes into breast milk, but it is not expected to harm your baby.
This is a plain-language summary of liothyronine's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and take your next dose at the regular time.
This is a plain-language summary of liothyronine's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store at room temperature between 68°F and 77°F.
Side Effects (from patient reports)
Based on 8,408 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for liothyronine, by number of reports
- Headache
Headache
859 reports
- Tiredness
Tiredness
816 reports
- Feeling sick to your stomach
Feeling sick to your stomach
569 reports
- Difficulty breathing
Difficulty breathing
549 reports
- Pain
Pain
469 reports
- High blood pressure
High blood pressure
461 reports
- Feeling unwell
Feeling unwell
431 reports
- Weight gain
Weight gain
431 reports
- Underactive thyroid
Underactive thyroid
426 reports
- Feeling strange
Feeling strange
411 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for liothyronine each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where liothyronine sits
liothyronine has more FDA adverse-event reports than 35% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is liothyronine; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 8,408 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
8,408
Reports Mentioning Death
195
2.3% of reports — not proof of cause
Hospitalization Reports
1,457
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 2 | HEADACHE | 859 |
| 3 | FATIGUE | 816 |
| 4 | NAUSEA | 569 |
| 5 | DYSPNOEA | 549 |
| 6 | PAIN | 469 |
| 7 | HYPERTENSION | 461 |
| 8 | MALAISE | 431 |
| 9 | WEIGHT INCREASED | 431 |
| 10 | HYPOTHYROIDISM | 426 |
| 11 | FEELING ABNORMAL | 411 |
| 12 | DIZZINESS | 385 |
| 13 | DIARRHOEA | 374 |
| 15 | ASTHMA | 354 |
| 16 | INSOMNIA | 351 |
| 17 | GASTROOESOPHAGEAL REFLUX DISEASE | 350 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
This medicine should not be used for weight loss or to treat obesity. Taking high doses of thyroid hormone for weight loss can cause serious and life-threatening side effects, especially when taken with stimulant medicines.
Known Drug Interactions
Other drugs: Amiodarone Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients.
Mechanism: This interaction can stop your body from turning one type of thyroid hormone into another, which can change your blood test results.
What to do: Your doctor may need to monitor your thyroid levels and adjust your medication if your blood tests change.
Administration of sertraline in patients stabilized on liothyronine sodium tablets may result in increased liothyronine sodium tablets requirements.
Mechanism: This antidepressant can lower the effectiveness of your thyroid medicine, meaning your body might need a higher dose.
What to do: Your doctor may need to increase your thyroid hormone dose if you are also taking this antidepressant.
Other drugs: Carbamazepine Furosemide (>80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein binding site displacement. Furosemide has been shown to inhibit the protein binding of T4 to TBG and albumin, causing an increased free-T4 fraction in serum. Furosemide competes for T4-binding sites on TBG, prealbumin, and albumin, so that a single high dose can acutely lower the total T4 level.
Mechanism: This water pill can knock thyroid hormones off the proteins they usually ride on in your blood, which changes the amount of active hormone in your body.
What to do: Your doctor should monitor your thyroid levels closely, especially if you are taking high doses of this water pill.
Drug or Drug Class Effect Beta-adrenergic antagonists (e.g., Propranolol >160 mg/day) In patients treated with large doses of propranolol (>160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are clinically euthyroid.
Mechanism: Taking high doses of this blood pressure medicine can change the amount of thyroid hormones found in your blood.
What to do: Your doctor may need to check your thyroid levels more frequently if you take a high dose of this medication.
7.5 Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and liothyronine sodium tablets may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.
Mechanism: Using these two drugs together can make both of them more powerful and increase the risk of side effects.
What to do: Your doctor should monitor you closely for side effects and may need to adjust your dosages.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can I use this medicine for weight loss?
What should I do if I experience chest pain?
How often will my doctor check my thyroid levels?
Can this medicine affect my blood sugar if I have diabetes?
What are the symptoms of taking too much of this medicine?
Can I take this medicine with other medications?
What if I have heart disease?
Can this medicine cause bone loss?
Is it safe to take this medicine during breastfeeding?
What happens if I stop taking this medicine?
What are the common side effects of liothyronine?
Does liothyronine interact with other medications?
What drug class is liothyronine?
Is there a generic version of liothyronine?
Is liothyronine safe during pregnancy?
Related Medications in Thyroid Hormone (T3)
Other drugs grouped near liothyronine - same-class peers and common alternatives.
levothyroxine
Synthroid, Levoxyl
Levothyroxine is a medicine that replaces a hormone normally made by your thyroid gland.
Compare with liothyronine →
methimazole
Tapazole
Methimazole (Tapazole) is a medicine that lowers the amount of thyroid hormone your body makes.
Compare with liothyronine →
propylthiouracil
PTU
Propylthiouracil (PTU) is a medicine that treats an overactive thyroid.
Compare with liothyronine →
thyroid (desiccated)
Armour Thyroid, Nature-Throid
Armour Thyroid is a natural thyroid hormone medicine.
Compare with liothyronine →
Medication Guides
Understanding Drug Interactions
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Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for liothyronine
The FDA label for liothyronine (sold under brand names such as Cytomel) classifies it as a prescription-only medication in the Thyroid Hormone (T3) class. This medicine treats hypothyroidism, a condition where your thyroid gland doesn't make enough thyroid hormone. Official labeling lists 18 commonly reported side effects, including Fatigue, Increased appetite, Weight loss.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 8,408 voluntary reports. The database also lists 17 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.27 versus $0.51 for the brand - a 47% generic savings.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: March 15, 2024
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages