Levothyroxine Dosage Calculator
Calculate starting levothyroxine dose for hypothyroidism treatment with clinical considerations
Calculate Levothyroxine Dosage
Used for ideal body weight calculation
Older patients typically need lower starting doses
Actual body weight (ideal weight used if overweight)
Used for ideal body weight calculation (Devine formula)
Clinical vs subclinical hypothyroidism affects dosing
Cardiac patients require lower starting doses
Critical Medical Warning
Levothyroxine dosing requires careful medical supervision and regular TSH monitoring. This calculator provides guidance only and cannot replace clinical judgment. Always consult an endocrinologist or physician for proper thyroid management.
Levothyroxine Administration Guidelines
Timing
• Morning: 30-60 minutes before breakfast
• Evening: At bedtime, 3+ hours after last meal
• Consistency: Same time daily for best results
• Empty stomach: Improves absorption significantly
Drug Interactions
• Iron supplements: Separate by 4+ hours
• Calcium/Antacids: Separate by 4+ hours
• Coffee: May reduce absorption
• Soy products: Can interfere with absorption
Monitoring Schedule
Initial Monitoring
TSH at 6-8 weeks
Dose Adjustment
Every 6-8 weeks until stable
Maintenance
TSH annually when stable
Hypothyroidism Symptoms
Fatigue & Weakness
Excessive tiredness, need for more sleep
Weight Gain
Unexplained weight gain despite normal diet
Cold Intolerance
Feeling cold when others are comfortable
Depression
Mood changes, difficulty concentrating
Important Safety Notes
Never adjust dose without medical supervision
TSH monitoring required every 6-8 weeks initially
Take consistently at same time daily
Empty stomach improves absorption
Cardiac patients need gradual dose escalation
Understanding Levothyroxine Therapy
What is Hypothyroidism?
Hypothyroidism occurs when the thyroid gland cannot produce sufficient thyroid hormones (T3 and T4) to meet the body's metabolic demands. The pituitary gland responds by releasing more TSH (thyroid-stimulating hormone), leading to elevated TSH levels.
Types of Hypothyroidism
- •Clinical: Low T4/FT4, High TSH, Symptomatic
- •Subclinical: Normal T4/FT4, High TSH, May be asymptomatic
Levothyroxine Dosing Principles
Weight-Based Dosing:
- • Adults (15-50): 1.6 mcg/kg/day (full replacement)
- • Adults (>50): 1.0-1.2 mcg/kg/day (lower start)
- • Cardiac patients: 0.5-1.0 mcg/kg/day (gradual)
- • Subclinical: 0.5-1.0 mcg/kg/day (conservative)
Clinical Pearls: Use ideal body weight for overweight patients. Round doses to nearest 12.5 mcg increment. Monitor TSH 6-8 weeks after starting or changing dose. Target TSH varies by age: 1-2 mU/L for younger, 2-4 mU/L for older adults.