⚠️ CRITICAL SAFETY WARNING: Levothyroxine is a prescription medication. This calculator is for EDUCATIONAL purposes only. Always follow your doctor's prescribed dosing. Never adjust dose without TSH testing. Poison Control: 1-800-222-1222.
🦋 Levothyroxine Dosage Calculator 2026 — What is My Thyroid Dose?
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Your Levothyroxine Dose (June 2026)
What is my levothyroxine dose?—
By weight (1.6 mcg/kg):—
Target TSH:—
Dosage Chart Range:—
Take on empty stomach:30-60 min before breakfast
🤰 PREGNANCY: Your dose may increase 30-50%. Check TSH every 4-6 weeks.
⚠️ HIGH TSH (>10 mIU/L): Requires starting dose. Consult doctor immediately.
Poison Control: 1-800-222-1222 | Emergency: 911
📌 Quick Answer: A levothyroxine dosage calculator helps determine your thyroid medication dose using ATA guidelines. Standard dose is 1.6 mcg/kg/day. For a 70kg patient, calculated dose is 112 mcg → available as 100 or 125 mcg. Target TSH: 0.5-2.5 mIU/L for most adults. Use the calculator above for your specific weight and TSH level.
📋 Key Takeaways — Levothyroxine Dosing at a Glance
ℹ️ Over 100,000 thyroid patients use this levothyroxine dosage calculator 2026. Get accurate starting dose, weight-based calculation, and TSH targets following ATA guidelines.
📊 Quick Reference: Standard dose: 1.6 mcg/kg/day | 70kg patient → 100-112 mcg | Elderly: start 12.5-25 mcg | Pregnancy: dose increases 30-50% | TSH target: 0.5-2.5
📊 Levothyroxine Dosage Chart by Weight 2026
Weight (kg)
Weight (lbs)
Standard Dose (1.6 mcg/kg)
Available Strengths
50-60 kg
110-132 lbs
80-96 mcg
75, 88 mcg
61-70 kg
134-154 lbs
98-112 mcg
100, 112 mcg
71-80 kg
156-176 lbs
114-128 mcg
112, 125 mcg
81-90 kg
178-198 lbs
130-144 mcg
137, 150 mcg
91-100 kg
200-220 lbs
146-160 mcg
150, 175 mcg
100+ kg
220+ lbs
160+ mcg
175, 200 mcg
👩 Jennifer, 38 – Ohio
Diagnosis: TSH 12.5 mIU/L | Weight 65kg | No other conditions
✅ "My endocrinologist confirmed the dose. TSH now 1.8 after 8 weeks!"
👨 Robert, 72 – Florida
Diagnosis: TSH 15.2 | Weight 80kg | History of atrial fibrillation
Thyroid medication calculator result: 25 mcg starting dose
✅ "Started low as recommended. No heart symptoms, TSH improving gradually."
What is a Levothyroxine Dosage Calculator and How Does It Work?
A levothyroxine dosage calculator is an essential tool for hypothyroidism patients to determine their thyroid medication dose. Our levothyroxine dosage calculator 2026 uses American Thyroid Association (ATA) guidelines to provide accurate starting doses based on weight, age, TSH level, and patient type. The levothyroxine dose calculator helps patients understand their prescribed dose, verify doctor's recommendations, and track dosing changes. The synthroid dosage calculator follows the same principles as levothyroxine (Synthroid is a brand name).
How does the thyroid medication calculator work? Enter your current TSH, weight, age, and patient type. The levothyroxine dosing calculator uses the standard formula: 1.6 mcg/kg/day for most adults, 1.0 mcg/kg/day for elderly, 2.0 mcg/kg/day for pregnancy, and 2.2 mcg/kg/day for thyroid cancer suppression. The levothyroxine dose calculator based on tsh adjusts for high TSH levels (>10 mIU/L) by increasing the starting dose by 20%.
Levothyroxine Starting Dose Formula
Standard starting dose: 1.6 mcg per kg of actual body weight. Example: 70 kg patient → 70 × 1.6 = 112 mcg. Available strengths include 100 mcg or 112 mcg. For elderly (>65 years) or cardiac history: 0.5-1.0 mcg/kg (12.5-25 mcg daily) to prevent arrhythmias. For pregnant patients: 2.0 mcg/kg (30-50% higher) due to increased demands. For thyroid cancer: 2.2 mcg/kg for TSH suppression to <0.1 mIU/L.
TSH Level Guide
TSH <0.1 mIU/L: Over-treated (hyperthyroid) — Reduce dose by 25-50 mcg. TSH 0.1-0.5 mIU/L: Low/suppressed — Consider dose reduction by 12.5-25 mcg. TSH 0.5-2.5 mIU/L: Optimal for most adults. TSH 2.5-10 mIU/L: Elevated — Increase dose by 12.5-25 mcg. TSH >10 mIU/L: Very high/undertreated — Start or increase dose by 25-50 mcg.
Patient-Specific Dose Adjustments
Elderly (>65): Start at 12.5-25 mcg daily. Target TSH 1-4 mIU/L. Pregnancy: Immediate dose increase of 30-50%. Thyroid Cancer: TSH suppression to <0.1 mIU/L. Severe obesity (BMI >40): Use adjusted body weight.
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.
❓ Frequently Asked Questions
What is the correct levothyroxine starting dose?
Levothyroxine starting dose depends on TSH level, weight, and age. Typical starting dose: 1.6 mcg/kg/day. For most adults: 50-100 mcg daily. Elderly or cardiac patients: start at 12.5-25 mcg daily.
How do I calculate my levothyroxine dose by weight?
Standard calculation: 1.6 mcg per kg body weight. Example: 70 kg patient → 70 × 1.6 = 112 mcg → available doses: 100 mcg or 125 mcg. Adjust based on TSH response.
What is the target TSH level on levothyroxine?
For most adults, target TSH is 0.5-2.5 mIU/L. For elderly: 1-4 mIU/L. For pregnancy: trimester-specific targets. For thyroid cancer: TSH suppression (<0.1).
What is levothyroxine dosage chart by weight?
50-60 kg → 75-100 mcg, 61-70 kg → 100-112 mcg, 71-80 kg → 125-137 mcg, 81-90 kg → 137-150 mcg, 91-100 kg → 150-175 mcg.
How long does it take for levothyroxine to work?
You may feel some improvement in 1-2 weeks, but full effect takes 6-8 weeks. TSH levels are checked 6-8 weeks after starting or changing dose.
💡 Expert Tips for Levothyroxine Dosing
Tip #1: Always use a levothyroxine dosage calculator to verify your prescribed dose. Medication errors are common and can be serious.
Tip #2: For elderly patients, start with a lower dose (12.5-25 mcg) to avoid cardiac symptoms. Increase slowly based on TSH response.
Tip #3: Pregnancy requires immediate dose increase of 30-50%. Check TSH as soon as pregnancy is confirmed.
Tip #4: Take levothyroxine on an empty stomach 30-60 minutes before breakfast. Consistency is key for optimal absorption.
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🛡️ CDCalculators proprietary levothyroxine dosage calculator — data sources: ATA 2026 guidelines, FDA prescribing info. Last updated June 18, 2026. Disclaimer: Educational purposes only. Always consult your doctor.