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Liothyronine (T3)

Oral tablet (5mcg, 25mcg), E4M capsule (5 to 25mcg)Available in all 50 states

Marketing purposes only. Actual medications, if prescribed, are dispensed by a licensed pharmacy.

thyroid

Liothyronine (T3)Liothyronine (T3)

Synthetic T3, the active thyroid hormone. Used as monotherapy or in combination with T4 for hypothyroidism optimization. E4M (extended 4-hour matrix) capsules provide slower release to avoid rapid T3 peaks.

Direct T3 supplementation bypasses conversion

Rapid onset of action

E4M formulations provide smoother levels

May improve symptoms in patients with impaired T4→T3 conversion

No commitment · HSA/FSA eligibleNo commitment · HSA/FSA eligible

How it works

Mechanism of action

T3 directly binds nuclear thyroid hormone receptors (TRα and TRβ), modulating transcription of genes controlling metabolic rate, thermogenesis, cardiac function, and neurodevelopment. 3 to 5x more potent than T4 with rapid onset.

The baseline panel.

Every Marek client receives this baseline panel before a provider review. Your provider may add additional biomarkers based on your health history, symptoms, and goals, pulling from 1,000+ available markers. See more biomarkers →

Hormone Profile

12 markers

Sex hormones

  • Total TestosteroneLC/MS
  • Free TestosteroneEquilibrium Dialysis
  • Estradiol, Sensitive / UltrasensitiveLC/MS
  • Sex Hormone Binding Globulin (SHBG)
  • ProgesteroneLC/MSFemale panel
  • Prolactin
  • Luteinizing Hormone (LH)
  • Follicle-Stimulating Hormone (FSH)
  • hCG, Total, QuantitativeFemale panel, pre-menopause

Adrenals & neurosteroids

  • Cortisol
  • DHEA-S

Growth hormone / IGF-1

  • Insulin-Like Growth Factor I (IGF-1)

Thyroid Status

3 markers

Thyroid hormones

  • Thyroid Stimulating Hormone (TSH)
  • Free T4
  • Free T3

Heart Health

9 markers

Cardiovascular health

  • Total Cholesterol
  • HDL Cholesterol
  • LDL Cholesterol
  • LDL:HDL Ratio
  • VLDL Cholesterol
  • Triglycerides
  • Apolipoprotein-B (ApoB)
  • C-Reactive Protein, High Sensitivity (hsCRP)
  • Lipoprotein(a) (Lp(a))

Metabolism

3 markers

Insulin sensitivity

  • Blood Glucose
  • Fasting Insulin
  • HbA1c

Organ Function

26 markers

Liver & pancreas

  • AST
  • ALT
  • Bilirubin, Total
  • γ-Glutamyl Transferase (GGT)

Kidney function

  • BUN
  • Creatinine w/ eGFR

Comprehensive Metabolic Panel (CMP)

  • Glucose
  • Blood Urea Nitrogen (BUN)
  • Creatinine
  • eGFR
  • BUN/Creatinine Ratio
  • Sodium
  • Potassium
  • Chloride
  • Carbon Dioxide, Total
  • Calcium
  • Protein, Total
  • Albumin
  • Globulin, Total
  • Albumin/Globulin (A/G) Ratio
  • Alkaline Phosphatase (ALP)
  • AST
  • ALT

Prostate health

  • Prostate-Specific Antigen (PSA)Male panel
  • Free PSAMale panel
  • % Free PSAMale panel

Nutrient Status

31 markers

Vitamins & minerals

  • Vitamin D, 25-OHD (25-Hydroxy)
  • Magnesium, RBC

Iron status

  • Iron
  • Iron Saturation
  • TIBC
  • UIBC
  • Ferritin

Complete Blood Count (CBC)

  • White Blood Count (WBC)
  • Red Blood Count (RBC)
  • Hemoglobin (Hgb)
  • Hematocrit (HCT)
  • MCV
  • MCH
  • MCHC
  • Red Cell Distribution Width (RDW)
  • Platelets
  • Neutrophils
  • Neutrophils (Absolute)
  • Lymphocytes
  • Lymphocytes (Absolute)
  • Neutrophil/Lymphocyte Ratio
  • Monocytes
  • Monocytes (Absolute)
  • Eosinophils
  • Eosinophils (Absolute)
  • Basophils
  • Basophils (Absolute)
  • Immature Cells
  • Immature Granulocytes
  • Immature Granulocytes (Absolute)
  • NRBC, w/ Reflex for Immature Cells

Clinical evidence

The research behind Liothyronine (T3).

Combination T4+T3 vs T4 Monotherapy: Meta-Analysis

Journal of Clinical Endocrinology & Metabolism (2006)

No consistent superiority of combination therapy in meta-analysis, but subset with DIO2 polymorphism showed significant preference and symptom improvement.

Safety profile

Monitoring & safety information.

Commonly reported side effects

  • Palpitations
  • Anxiety
  • Tremor
  • Insomnia
  • Diarrhea

Less common but serious risks

  • Cardiac arrhythmias (atrial fibrillation)
  • Angina/MI (in cardiac patients)
  • Bone loss with chronic excess

Generally not appropriate for

  • Thyrotoxicosis
  • Uncorrected adrenal insufficiency
  • Acute MI/angina

Typical monitoring

  • TSH, free T3, free T4 (every 6 to 8 weeks during titration)
  • Heart rate and rhythm
  • Bone density (long-term)

FAQ

Quick answers.

Synthetic T3, the active thyroid hormone. Used as monotherapy or in combination with T4 for hypothyroidism optimization. E4M (extended 4-hour matrix) capsules provide slower release to avoid rapid T3 peaks.
Direct T3 supplementation bypasses conversion. Rapid onset of action. E4M formulations provide smoother levels. May improve symptoms in patients with impaired T4→T3 conversion.
Common side effects include: palpitations, anxiety, tremor, insomnia, diarrhea. Most side effects are dose-dependent and may resolve with continued use or dose adjustment.
View all FAQs
See all FAQs

Synthetic T3, the active thyroid hormone. Used as monotherapy or in combination with T4 for hypothyroidism optimization. E4M (extended 4-hour matrix) capsules provide slower release to avoid rapid T3 peaks.

Treatments are dependent on licensed clinical prescription. Client costs vary based on individual labs and panel in treatments and services.