liothyronine
Brand names: Cytomel
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.
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.
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.
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.
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.
Storage
Store at room temperature between 68°F and 77°F.
Side Effects (from patient reports)
Based on 5,947 FDA adverse event reports.
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
Death-Related Reports
195
Hospitalization Reports
1,457
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DRUG INEFFECTIVE | 936 |
| 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 |
| 14 | OFF LABEL USE | 361 |
| 15 | ASTHMA | 354 |
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.
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 →
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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 5,947 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.
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