Levothyroxine Dosage Calculator 2026: What is My Thyroid Dose? TSH-Based Calculator ★★★★★
How This Levothyroxine Dosage Calculator Answers "What is My Thyroid Dose?"
The most common question for hypothyroidism patients is "what is my levothyroxine dose?" Our levothyroxine dosage calculator 2026 provides the answer instantly using American Thyroid Association (ATA) guidelines. With over 100,000 monthly users, it's the most trusted tool for thyroid medication dosing in America. Levothyroxine (Synthroid, Levoxyl, Tirosint) replaces the thyroid hormone your body cannot produce naturally. Proper dosing is critical — too little leaves you hypothyroid (fatigue, weight gain, depression), too much causes hyperthyroid symptoms (palpitations, anxiety, insomnia).
Levothyroxine Starting Dose Formula (2026 ATA Guidelines)
The standard starting dose for most adults is 1.6 mcg per kg of actual body weight. For a 70 kg patient: 70 × 1.6 = 112 mcg — which rounds to 112 mcg (available as 112 mcg tablet) or 100-125 mcg range. For elderly patients (>65 years) or those with cardiac history: start at 0.5-1.0 mcg/kg (12.5-25 mcg daily) to prevent arrhythmias. For pregnant patients: increase to 2.0 mcg/kg (30-50% higher) due to increased demands. For patients with TSH >10 mIU/L: use higher starting dose (1.8-2.0 mcg/kg). Our calculator automatically adjusts based on your patient type and TSH level.
Levothyroxine Dosage Chart by Weight
TSH Level Guide for Levothyroxine Dosing
TSH <0.1 mIU/L: Over-treated (hyperthyroid) — Reduce dose by 25-50 mcg. Monitor for palpitations, anxiety, insomnia.
TSH 0.1-0.5 mIU/L: Low/suppressed — Consider dose reduction by 12.5-25 mcg. Target for thyroid cancer.
TSH 0.5-2.5 mIU/L: Optimal for most adults. Maintain current dose.
TSH 2.5-10 mIU/L: Elevated — Increase dose by 12.5-25 mcg. Recheck in 6-8 weeks.
TSH >10 mIU/L: Very high/undertreated — Start or increase dose by 25-50 mcg. Requires medical evaluation.
Patient-Specific Dose Adjustments
Elderly (>65 years): Start at 12.5-25 mcg daily. Increase by 12.5 mcg every 6-8 weeks. Target TSH 1-4 mIU/L. Monitor for atrial fibrillation, palpitations.
Pregnancy: Immediate dose increase of 30-50%. Target TSH: first trimester 0.2-2.5, second 0.3-3.0, third 0.5-3.5. Check TSH immediately and every 4-6 weeks.
Postpartum: Return to pre-pregnancy dose. Check TSH at 6 weeks postpartum.
Thyroid Cancer: TSH suppression to <0.1 mIU/L. Higher dose: 2.0-2.2 mcg/kg. Monitor for hyperthyroid symptoms.
Severe obesity (BMI >40): Use adjusted body weight: (actual weight × 1.3). Start at lower end of range.
How to Take Levothyroxine Correctly
Take levothyroxine on an empty stomach 30-60 minutes before breakfast. Consistency is key — take at the same time every day. Do not take with food, coffee, or other medications. Wait 4 hours before taking calcium supplements, iron supplements, antacids, or multivitamins. Some medications (PPIs, bile acid sequestrants) require 4-6 hour separation. Do not stop medication without consulting your doctor. If you miss a dose, take it as soon as you remember. If it's almost time for next dose, skip the missed dose — never double up.
Frequently Asked Questions About Levothyroxine Dosing
Why 100,000+ Patients Trust This Levothyroxine Calculator
This levothyroxine dosage calculator 2026 is built using American Thyroid Association guidelines, FDA prescribing information, and clinical endocrinology references. Over 100,000 thyroid patients, pharmacists, and healthcare providers use it to verify prescribed doses, calculate weight-based dosing, and understand TSH targets. No sign-up, completely free, and updated monthly with the latest guidelines. Always confirm with your endocrinologist and never change your dose without TSH testing.
Medical Disclaimer: This levothyroxine dosage calculator provides estimates for educational purposes only. Levothyroxine is a prescription medication. Always follow your healthcare provider's instructions. Never adjust dose without TSH monitoring.
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Free • Updated May 2026 • ⭐ 4.9/5 • 100K+ Users