At a glance
Effects
- Raised metabolic rate: Enhances oxygen consumption across most body tissues, increasing basal metabolic rate and accelerating carbohydrate, lipid, and protein turnover [4].
- Faster onset than T4: Onset within a few hours; maximum response in 2–3 days, making it the fastest-acting oral thyroid hormone [5].
- TSH suppression: Suppresses pituitary TSH secretion, used therapeutically to manage thyroid cancer recurrence risk or to diagnose mild hyperthyroidism [2].
- Cardiovascular stimulation: Increases heart rate, ventricular contractility, and cardiac output, and decreases total systemic vascular resistance [6].
- CNS and thermogenic activity: Increases the rate of cerebration, gastrointestinal motility, and thermogenesis via marked increases in basal metabolic rate and mitochondrial activity [6].
Synthetic thyroid hormone (T3)
~2.5 days
Oral (tablet); IV for emergencies
Within a few hours; peak 2–3 days
Narrow — careful titration required
About Liothyronine Sodium
Every point here is drawn from public medical and harm-reduction sources. A bracketed number after a claim — like [1]— is a reference: tap it to open the exact source it's based on (numbered list at the bottom). It is not a rating or score. Educational information, not medical advice.
Product specifics
- Est. delivery
- 3–7 business days · EU tracked
Product details as stated by the vendor (claims, not independently verified). Delivery is our standard EU estimate.
What it is
Liothyronine sodium (T3, brand name Cytomel) is a synthetic thyroid hormone identical to the triiodothyronine naturally produced by the thyroid gland [1]. It is used medically as replacement therapy for hypothyroidism, TSH suppression in thyroid cancer, and as a diagnostic aid; it is also encountered in performance contexts for its metabolic rate-raising effects [2].
How it works
Liothyronine acts at the cellular level by diffusing into the cell nucleus and binding to thyroid hormone receptors attached to DNA [3]. This hormone–receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins [3], which collectively raise the basal metabolic rate and enhance oxygen consumption and the metabolism of carbohydrates, lipids, and proteins across virtually all body tissues [4]. Because T3 is not firmly bound to serum proteins it is rapidly available to tissues, producing onset of action within a few hours and peak pharmacological effect within 2–3 days — substantially faster than levothyroxine (T4), which first requires peripheral conversion to T3 [5].
Risks & side effects
Most important: The most critical risk is cardiovascular toxicity from overtreatment: excess liothyronine can raise heart rate, increase cardiac wall thickness and contractility, and precipitate angina, arrhythmias, heart failure, myocardial infarction, or cardiac arrest — particularly in elderly patients or those with pre-existing cardiovascular disease [7]. Wide swings in serum T3 levels following each dose amplify this danger compared with T4-based therapy [8].
Common
Serious
- Cardiac arrhythmias — can occur at any dose in susceptible individuals [7]
- Angina pectoris or precipitation of acute coronary events [7]
- Heart failure in patients with underlying cardiac disease [7]
- Atrial fibrillation — increased risk in elderly and those with cardiovascular disease [9]
- Acute adrenal crisis if initiated without glucocorticoid cover in adrenal insufficiency [10]
- Adverse effects on bone metabolism (reduced bone density) with chronic overtreatment [11]
Safety & harm reduction
- Uncorrected adrenal insufficiency — risk of acute adrenal crisis [10]
- Untreated thyrotoxicosis [12]
- Acute myocardial infarction uncomplicated by hypothyroidism [12]
- Hypersensitivity to liothyronine sodium or any formulation component [12]
- Do NOT use for obesity or weight loss in euthyroid individuals — ineffective and dangerous [13]
- Do NOT use oral liothyronine to treat myxedema coma — IV formulation required [9]
- Serum T3 levels and TSH (note: TSH unreliable in secondary/tertiary hypothyroidism — use serum T3) [5]
- Heart rate, blood pressure, and cardiac rhythm — especially on initiation and at each dose increase [7]
- Cardiac arrhythmia monitoring during surgical procedures in CAD patients on suppressive therapy [14]
- Bone mineral density with long-term use — overtreatment suppresses bone formation [11]
- Blood glucose and lipid profile — thyroid hormone alters carbohydrate and lipid metabolism [11]
- Thyroid function tests 4–8 weeks postpartum in pregnant patients [15]
- Oral anticoagulants (e.g. warfarin) — liothyronine potentiates anticoagulant effect; dose reduction may be needed [13]
- Tricyclic and tetracyclic antidepressants — combined use increases cardiac arrhythmia risk and CNS stimulation [3]
- Sympathomimetic agents (e.g. adrenaline/ephedrine) — increased risk of coronary insufficiency [14]
- Antacids, calcium, iron supplements, cholestyramine — bind T3 in gut and reduce absorption; separate by at least 4 hours [13]
- Glucocorticoids — thyroid hormones accelerate glucocorticoid clearance; adrenal insufficiency may be unmasked [10]
- Sertraline — may increase liothyronine dose requirements [3]
- Furosemide and salicylates — displace T3/T4 from protein binding, transiently altering free hormone levels [5]
- Always start at the lowest effective dose and titrate upward slowly (e.g. 5 mcg/day, increasing by 5–25 mcg every 1–2 weeks as tolerated) [16]
- Patients with cardiovascular disease: start at 5 mcg/day and increase by no more than 5 mcg every 2 weeks under cardiac supervision [16]
- When switching from levothyroxine or desiccated thyroid: discontinue the prior medication first, start liothyronine at low dose, and anticipate residual T4 effects for several weeks [17]
- If cardiovascular symptoms worsen, withhold dose for one week and restart at a lower level [10]
- Do not use to treat obesity or infertility in euthyroid patients [13]
Dosage context
Prescription dosing (commonly reported, not a personal prescription): for hypothyroidism, the recommended starting dose is 25 mcg once daily, increasing by 25 mcg every 1–2 weeks as needed; usual maintenance is 25–75 mcg once daily [16]. For patients with cardiovascular disease, starting at 5 mcg daily with 5 mcg increments every two weeks is standard [16]. The half-life of approximately 2.5 days means once-daily dosing is feasible, though serum T3 peaks and troughs are more pronounced than with T4 therapy [18]. These are medically established ranges — self-dosing outside supervised clinical care is hazardous given the drug's narrow therapeutic index [11].
Sources
- 1.DrugBank — Liothyronine: Uses, Interactions, Mechanism of Action
- 2.MedCentral — Liothyronine: uses, dosing, warnings, adverse events, interactions
- 3.DailyMed (Pfizer label) — Liothyronine Sodium: DNA transcription mechanism
- 4.DailyMed — Liothyronine Sodium Tablets USP (basal metabolic rate, oxygen consumption)
- 5.Pfizer Cytomel Prescribing Information (onset, protein binding, pharmacokinetics)
- 6.Drugs.com — Liothyronine Package Insert (cardiovascular effects, heart rate, contractility)
- 7.DailyMed NIH — Liothyronine Sodium Tablet (adverse reactions, cardiac arrest, arrhythmias)
- 8.DailyMed — Liothyronine Sodium (T3 serum swings, cardiovascular counterbalance)
- 9.DailyMed — Liothyronine Sodium Tablet (atrial fibrillation, cardiac adverse reactions, myxedema coma)
- 10.RxList — Cytomel (Liothyronine Sodium): adrenal insufficiency, interactions, contraindications
- 11.Pfizer Cytomel Prescribing Information — narrow therapeutic index, bone, growth effects
- 12.RxList — Liothyronine: contraindications (thyrotoxicosis, acute MI, hypersensitivity)
- 13.DailyMed — Liothyronine Sodium 5 mcg (obesity warning, anticoagulant interaction, dosing)
- 14.ClinicalTrials — Acute Effects of Liothyronine on Cardiovascular System (arrhythmia monitoring)
- 15.DailyMed — Liothyronine Sodium (postpartum TSH monitoring)
- 16.Drugs.com — Liothyronine Dosage Guide (25 mcg starting dose, 25–75 mcg maintenance)
- 17.DailyMed — Liothyronine Sodium Tablets USP (switching from T4, residual effects)
- 18.ScienceDirect — Liothyronine Sodium overview (half-life ~2.5 days, once-daily dosing)
This information is provided for educational and harm-reduction purposes only. It is not medical advice. These substances can carry serious health risks; effects and safe use vary by individual. Consult a qualified healthcare professional before use. Legal status varies by country — it is your responsibility to know your local law. We do not encourage misuse.
Other options for Liothyronine Sodium· 9 offers
Same compound from different labs/brands and pack sizes. Tap a row to switch brand — the price and buy button update instantly.
This compound comes in different forms (e.g. injectable vs oral vs topical). Cost per mg is only comparable within the same form.
| Brand | Form | Strength | Pack | Price | Per mg |
|---|---|---|---|---|---|
Generic | blister-pack | 25 mcg/tab | 37,90 € | — | |
Generic | blister-pack | 25 mcg/tab | 60 tab | 54,90 € | — |
Generic | vial | 200 mcg/ml | 50 ml | 84,90 € | — |
Abdi İbrahim | blister-pack | 25 mcg/tab | 400 tab | 98,90 € | — |
Generic | blister-pack | 25 mcg/tab | 400 tab | 98,90 € | — |
Intex PharmaSelected | blister-pack | 25 mcg/tab | 100 tab | 99,99 € | — |
Generic | oral-liquid | 200 mcg/ml | 100 ml | 179,99 € | — |
Generic | — | — | 179,99 € | — | |
Generic | blister-pack | 20 mcg/tab | 100 tab | 184,99 € | — |