medicationPrescription only (US)Liothyronine (synthetic T3) is FDA-approved for hypothyroidism; its use in combination with levothyroxine remains an area of active clinical trial investigation rather than a settled first-line recommendation
LiothyronineBenefits, Dosage & Interactions
Also known as: T3, Cytomel
Liothyronine, also known by its chemical abbreviation T3, is a synthetic form of the naturally occurring thyroid hormone triiodothyronine. It is available as a prescription medication and is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones.
Researched by DoseRoutine R&D TeamReviewed for accuracy by Nicholas Alexander, RSELast updated
Evidence: Strong — 2 human randomized trials and regulatory approval on file.
Evidence strengthStrong · 4/4
PreclinicalStrong human evidence
2 human randomized trials and regulatory approval on file.
Plasma half-life
~25 h
Typical timing
morning
Food rule
empty stomach
Default unit
mcg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
- Reported amounts
- Added to levothyroxine as a fixed T4:T3 combination in the LEVOLIO study (totally thyroidectomized subjects); the Azizi et al. protocol describes a slow-release liothyronine formulation combined with levothyroxine, with the completed comparative-effectiveness trial titrating levothyroxine+liothyronine combinations to a target TSH[1][2][3]
Reported for Liothyronine in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the Liothyronine entry is written from. Each number matches an inline marker above.
- [1]Randomized double-blind placebo-controlled trial on levothyroxine and liothyronine combination therapy in totally thyroidectomized subjects: the LEVOLIO studyBrigante G, Santi D, Boselli G, Margiotta G, Corleto R, Monzani ML, Craparo A, Locaso M, Sperduti S, Roy N, Casarini L, Trenti T, Tagliavini S, De Santis MC, Roli L, Rochira V, Simoni M · European Journal of Endocrinology · 2024 · Peer-reviewed · PMID 38124252
- [2]Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in HypothyroidismShakir MKM, Brooks DI, McAninch EA, Fonseca TL, Mai VQ, Bianco AC, Hoang TD · The Journal of Clinical Endocrinology & Metabolism · 2021 · Peer-reviewed · PMID 34185829
- [3]Treatment of hypothyroidism with levothyroxine plus slow-release liothyronine: a study protocol for a randomized controlled double-blinded clinical trialAzizi F, Amouzegar A, Abdi H, Tohidi M, Masoumi S, Khalili D, Mehrabi Y, Zadehvakili A, Hedayati M, Momenan AA, Mehran L · Trials · 2025 · Peer-reviewed · PMID 40598574
How to track Liothyronine doses
Tracking Liothyronine well takes four fields and a habit. Here is what to record so the log is still useful in three months.
- 1
Add the dose and unit
Log Liothyronine with its dose in mcg so totals stay comparable over time — including days when you split the dose or skip it.
- 2
Set the time of day and food rule
Typical timing is morning. Take it on an empty stomach, and record it that way so absorption stays consistent. Reminders fire at that time and can export to your calendar.
- 3
Check it against the rest of the stack
Run Liothyronine through the interaction checker against everything else in the routine — supplements, peptides, hormones and prescriptions — before it becomes a daily habit.
- 4
Log adherence, not intentions
Mark each dose taken, skipped or delayed as it happens. Weeks of honest logs are what make an adherence rate or a trend line meaningful; retrospective guessing is not.
- 5
Review against outcomes
With a reported half-life around 25 h, effects and timing shifts show up over days rather than instantly. Review Liothyronine alongside your logged metrics and any relevant blood work every few weeks before changing the dose.
What to log each time
- Dose in mcg
- Time of day and whether it was taken on an empty stomach
- Taken / skipped / delayed
- Any side effects or notable changes
References & Evidence
Sources on this page that document Liothyronine dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Liothyronine?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Liothyronine, also known by its chemical abbreviation T3, is a synthetic form of the naturally occurring thyroid hormone triiodothyronine. It is available as a prescription medication and is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones. Unlike levothyroxine (T4), which is a prohormone that needs to be converted into T3 by the body, liothyronine is the active form of the hormone, leading to a faster onset of action and elimination.
Historically, liothyronine has been used alone or in combination with levothyroxine for thyroid hormone replacement therapy. It is also used in the diagnosis of hyperthyroidism (an overactive thyroid gland) and as an adjunct to surgery and radioiodine therapy in the management of thyroid cancer. While not directly indicated for weight loss, its role in metabolism has led to some off-label discussions regarding its effects on body weight, particularly in complex thyroid cases. The medication is typically taken orally in tablet form.
What does the research say about Liothyronine?
Tap a section to expand.
Liothyronine (T3) exerts its physiological effects by binding to specific thyroid hormone receptors located within the nucleus of cells throughout the body. Once bound, the T3-receptor complex interacts with DNA, modulating gene expression. This regulation of gene expression influences a wide array of metabolic processes, including energy production, protein synthesis, fat metabolism, and carbohydrate utilization. By increasing the synthesis of various enzymes and structural proteins, T3 plays a crucial role in maintaining normal metabolic rate, body temperature, cardiovascular function, and central nervous system development and activity. Because T3 is the most metabolically active form of thyroid hormone, its administration directly provides the active hormone required for cellular function, bypassing the need for peripheral conversion from T4. This direct action contributes to liothyronine's rapid onset and offset of effects compared to levothyroxine (T4). (Source: PubChem, DrugBank)
Source for this section: Sources for How does Liothyronine work?: Jumps to this entry in the sources and references list at the end of the page.
The primary benefit of liothyronine is its effectiveness in treating hypothyroidism, a condition characterized by insufficient thyroid hormone production. For individuals with hypothyroidism, liothyronine replacement therapy helps to restore normal metabolic function, alleviating symptoms such as fatigue, weight gain, cold intolerance, constipation, dry skin, and depression. Its direct action as the active T3 hormone may be particularly beneficial for patients who have impaired conversion of T4 to T3, though this is a subject of ongoing clinical debate and research. (Source: NIH ODS, DrugBank)
In specific diagnostic contexts, liothyronine can be used in a T3 suppression test to help diagnose hyperthyroidism by evaluating the thyroid gland's responsiveness to negative feedback. It also plays a role as an adjunct therapy in the management of thyroid cancer, particularly during preparation for radioactive iodine scanning and treatment, by elevating TSH levels (thyroid-stimulating hormone) which helps in the uptake of iodine by remaining thyroid cancer cells after surgery. (Source: FDA label)
Clinical evidence for liothyronine's efficacy in hypothyroidism primarily stems from its long-standing use and biological plausibility as a direct thyroid hormone replacement. While levothyroxine (T4) is generally considered the standard first-line treatment, some studies and clinical practice suggest that a subset of patients may benefit from combination therapy with both levothyronine and liothyronine. A Cochrane review on combination T4 and T3 hormone replacement therapy found that some patients reported improvements in mood and quality of life measures with combination therapy compared to T4 monotherapy, although these findings were not consistently replicated across all studies and effects on body weight or thyroid-related symptoms were often not significantly different. (Source: Cochrane)
Research continues to explore optimal dosing strategies and identifying specific patient populations who may respond better to T3-containing regimens. The FDA label provides detailed information on its approved indications and safety profile, reflecting the extensive clinical data supporting its use in thyroid disorders. (Source: FDA label)
Side effects of liothyronine are typically associated with excessive dosage, mimicking symptoms of hyperthyroidism. These can include:
* Palpitations, increased heart rate (tachycardia), and other cardiac arrhythmias
* Chest pain (angina)
* Nervousness, tremors, irritability
* Insomnia
* Increased sweating
* Heat intolerance
* Weight loss (often unintended and rapid)
* Diarrhea
* Muscle weakness and cramps
* Headache
* Changes in menstrual cycle
Symptoms of over-treatment should be reported to a clinician immediately. Acute massive overdosage can be life-threatening, especially in patients with pre-existing heart conditions. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Liothyronine should be used with caution in patients with known cardiovascular disease, including angina, coronary artery disease, and arrhythmias, as thyroid hormones can increase cardiac work and oxygen demand. In older patients or those with a history of heart disease, dosage initiation should be lower and titration gradual. Patients with adrenal insufficiency should have this condition treated before initiating liothyronine, as thyroid hormone replacement can precipitate an acute adrenal crisis. Thyroid hormones are not indicated for the treatment of obesity or for weight reduction in euthyroid (normal thyroid function) patients; doses within the physiological range are ineffective for weight reduction, and larger doses may produce serious or even life-threatening toxicity, particularly when given in conjunction with other anorectic drugs. Extreme caution should be exercised in patients with diabetes mellitus or diabetes insipidus, as thyroid hormone therapy may alter requirements for insulin or oral antidiabetic agents.
Regular monitoring of thyroid function tests (TSH, free T3) is essential to ensure appropriate dosing and prevent over-treatment or under-treatment. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Liothyronine is contraindicated in individuals with uncorrected adrenal insufficiency, as thyroid hormone administration can worsen this condition. It is also contraindicated in cases of diagnosed but untreated thyrotoxicosis (hyperthyroidism from any cause) due to the risk of exacerbating symptoms and potential cardiac complications. Patients with hypersensitivity to liothyronine or any component of the formulation should also avoid its use. Use in conjunction with drugs for weight loss, especially at supraphysiological doses, is contraindicated due to the risk of severe and potentially fatal adverse effects. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Several medications can interact with liothyronine, potentially altering its effectiveness or increasing the risk of adverse effects:
* **Anticoagulants (e.g., warfarin):** Thyroid hormones can increase the anticoagulant effect, potentially leading to an increased risk of bleeding. Close monitoring of INR and dose adjustment may be necessary.
* **Digitalis glycosides:** The effects of digitalis may be decreased in hypothyroid patients and enhanced by thyroid hormone replacement.
* **Antidiabetic agents (e.g., insulin, oral hypoglycemics):** Thyroid hormones can increase blood glucose levels, potentially requiring adjustments in antidiabetic medication dosages.
* **Cholestyramine and colestipol:** These bile acid sequestrants can bind to thyroid hormones in the gastrointestinal tract, reducing their absorption. Liothyronine should be taken several hours apart from these medications.
* **Estrogen-containing oral contraceptives and estrogen replacement therapy:** Estrogens can increase thyroid binding globulin (TBG), requiring an increased dose of liothyronine.
* **Tricyclic antidepressants (e.g., imipramine, amitriptyline):** Co-administration may increase the risk of cardiac arrhythmias and toxicity.
* **Beta-blockers (e.g., propranolol, metoprolol):** Effectiveness of beta-blockers may be altered.
* **Corticosteroids:** Thyroid hormones can increase the metabolic clearance of corticosteroids.
Always inform your healthcare provider about all medications, supplements, and herbal products you are taking to identify potential interactions. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Liothyronine is typically taken once daily, usually in the morning. This timing helps to mimic the body's natural diurnal rhythm of thyroid hormone release and minimize potential sleep disturbances that could arise from taking it later in the day. It is often recommended to take liothyronine on an empty stomach, at least 30 minutes to an hour before food or other medications, to ensure optimal absorption. Consistency in timing and relation to meals is important for maintaining stable thyroid hormone levels. The specific dose and timing must be set by a licensed clinician.
Source for this section: Sources for When should you take Liothyronine?: Jumps to this entry in the sources and references list at the end of the page.
What interacts with Liothyronine?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any supplement + medication | Note | Category ruleConfidence: theoretical | Some supplements change how the body processes medications (absorption, liver enzymes, or additive effects).Source pending | Specific pairs are checked against a licensed drug database and shown with their own severity. Always confirm with your provider or pharmacist. |
| Any vitamin + medication | Note | Category ruleConfidence: theoretical | Certain vitamins interact with specific medications (e.g., vitamin K with blood thinners).Source pending | Specific pairs are checked against a licensed source; confirm with your provider. |
| Calcium | Caution | Compound pairConfidence: theoretical | Minerals chelate T3 and reduce absorption.Source pending | Separate liothyronine and mineral supplements by at least 4 hours.Suggested separation: 4 h |
| Iron (ferrous bisglycinate) | Caution | Compound pairConfidence: theoretical | Minerals chelate T3 and reduce absorption.Source pending | Separate liothyronine and mineral supplements by at least 4 hours.Suggested separation: 4 h |
| Magnesium Glycinate | Caution | Compound pairConfidence: theoretical | Minerals chelate T3 and reduce absorption.Source pending | Separate liothyronine and mineral supplements by at least 4 hours.Suggested separation: 4 h |
Frequently asked questions about Liothyronine
Liothyronine is a medication. It is also known as T3 and Cytomel. The references summarized come from NIH and PubMed records, FDA labeling where it exists, and Mayo Clinic patient material.
Liothyronine is commonly discussed in the context of the goals discussed on its profile page. Individual response varies, and use should be reviewed with a licensed clinician who can weigh the benefits and risks for your situation.
For Liothyronine, it is typically taken in the morning, it is usually taken on an empty stomach, and its approximate half-life is 25 hours, which influences dosing frequency. Always follow the specific dose your clinician or the product label prescribes.
Liothyronine carries potential side effects and drug interactions, documented in NIH, Mayo Clinic, and FDA label sources. Stop use and contact a clinician if you experience unexpected symptoms.
As a medication, Liothyronine can overlap with other supplements, prescription medicines, hormones and peptides. Because Liothyronine is usually taken in the morning, most avoidable conflicts come from what else lands in that same window. With a reported plasma half-life near 25 hours, separating doses can change the picture as much as removing one. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Liothyronine with no sign-up.
Whether Liothyronine fits alongside testosterone replacement therapy depends on the protocol — dose, ester and ancillaries such as HCG or anastrozole — and on current bloodwork. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
"Peptides" is not one category — healing peptides, GLP-1 agonists, growth-hormone secretagogues and melanocortins each behave differently next to Liothyronine. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
With a plasma half-life near 25 hours, once-daily dosing is the usual pattern for Liothyronine. It is typically taken in the morning. Most protocols have it taken on an empty stomach. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
With a plasma half-life near 25 hours, a single missed dose of Liothyronine usually has a smaller effect on overall exposure than an irregular pattern of missed doses does. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Liothyronine the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 23724940(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/23724940
Verify at
Publisher search links for Liothyronine. These are places to check the information — they are not citations, so they are not numbered.
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Liothyronine?
Plain-text summary, safe to quote verbatim:
Liothyronine, also known by its chemical abbreviation T3, is a synthetic form of the naturally occurring thyroid hormone triiodothyronine. It is available as a prescription medication and is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones.
Source: DoseRoutine — https://doseroutine.com/library/liothyronine
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Liothyronine — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/liothyronine
What compounds are similar to Liothyronine?
Others in the medication category or studied for the same goals.