Levothyroxine Dosage & Adjustment Calculator

Personalized thyroid hormone dose for every patient

Calculate the optimal levothyroxine (T4) dose for hypothyroidism, elderly, cardiac patients, and more. Adjust dose by weight, age, and clinical scenario.

Levothyroxine Dosage Examples

See how dosage changes with different scenarios.

Healthy Adult, 70 kg

Healthy Adult

Standard starting dose for a healthy adult with hypothyroidism.

Body Weight (kg): 70

Age (years): 35

Clinical Scenario: Healthy Adult (No Cardiac Disease)

Elderly, 60 kg

Elderly

Lower starting dose for an elderly patient.

Body Weight (kg): 60

Age (years): 72

Clinical Scenario: Elderly (>65 years)

Cardiac Disease, 80 kg

Cardiac Disease

Conservative dose for a patient with cardiac disease.

Body Weight (kg): 80

Age (years): 68

Clinical Scenario: Cardiac Disease (e.g. CAD, arrhythmia)

Subclinical Hypothyroidism, 65 kg

Subclinical Hypothyroidism

Lower dose for subclinical hypothyroidism.

Body Weight (kg): 65

Age (years): 40

Clinical Scenario: Subclinical Hypothyroidism

Other Titles
Understanding Levothyroxine Dosage & Adjustment Calculator: A Comprehensive Guide
Everything you need to know about safe and effective thyroid hormone dosing.

What is Levothyroxine Dosage & Adjustment?

  • Levothyroxine and Thyroid Hormone Replacement
  • Why Accurate Dosing Matters
  • Who Needs Dose Adjustment?
Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4), used to treat hypothyroidism. Accurate dosing is crucial to restore normal metabolism and avoid complications.
Levothyroxine in Clinical Practice

Clinical Examples

  • A 70 kg adult with hypothyroidism typically starts at 112 mcg/day.
  • An elderly patient may require only 50 mcg/day initially.

Step-by-Step Guide to Using the Calculator

  • Input Patient Data
  • Select Clinical Scenario
  • Interpret Results
Enter the patient's weight, age, and select the clinical scenario. The calculator will recommend a starting dose and suggest tablet strengths.
How to Use the Calculator

Usage Examples

  • Entering 80 kg, 45 years, healthy adult yields 128 mcg/day.
  • Cardiac patients get a lower starting dose, e.g., 40 mcg/day.

Real-World Applications of Levothyroxine Dosing

  • Primary Hypothyroidism
  • Subclinical Hypothyroidism
  • Special Populations
Levothyroxine dosing is used in primary and subclinical hypothyroidism, post-thyroidectomy, and in special populations like elderly or cardiac patients.
Clinical Applications

Application Examples

  • Post-thyroidectomy patients may need full replacement doses.
  • Subclinical cases often start with 25-50 mcg/day.

Common Misconceptions and Correct Methods

  • Myth: One Dose Fits All
  • Myth: Higher Dose is Better
  • Correct: Individualized Dosing
Dosing must be individualized. Over- or under-treatment can cause serious health issues. The calculator helps avoid common mistakes by personalizing recommendations.
Avoiding Dosing Errors

Misconception Examples

  • A 90 kg adult should not automatically get 150 mcg/day.
  • Elderly or cardiac patients need much lower starting doses.

Mathematical Derivation and Examples

  • Dose per kg Calculation
  • Tablet Splitting and Rounding
  • Adjusting for TSH Targets
The standard formula is: Dose (mcg) = Weight (kg) × Dose per kg (mcg/kg). Tablet suggestions are based on common strengths (e.g., 25, 50, 75, 100 mcg). Dose can be adjusted for TSH targets if provided.
Calculation Formula

Mathematical Examples

  • A 60 kg elderly patient: 60 × 1.0 = 60 mcg/day (rounded to 50 or 75 mcg tablet).
  • A 70 kg healthy adult: 70 × 1.6 = 112 mcg/day (rounded to 100 or 125 mcg tablet).