This levothyroxine dosage calculator is designed to assist healthcare providers in determining the appropriate dose of levothyroxine for patients suffering from hypothyroidism.
Consider a 45-year-old woman weighing 70 kg with newly diagnosed hypothyroidism. The calculator might suggest an initial dose of 1.6 μg/kg/day, leading to a starting dose of 112 μg daily.
This recommendation acts as a starting point, which can be adjusted based on subsequent thyroid function tests and clinical response.
Levothyroxine Dosage Calculator
| Patient | Weight (kg) | Age | Calculation | Recommended Dose (μg/day) | Conversion to mg |
|---|---|---|---|---|---|
| Adult 1 | 75 | 40 | 75 × 1.7 μg/kg/day | 127.5 (rounded to 125) | 0.125 mg |
| Adult 2 | 90 | 35 | 90 × 1.6 μg/kg/day | 144 | 0.144 mg |
| Elderly | 65 | 72 | 65 × 1.0 μg/kg/day | 65 | 0.065 mg |
| Child | 30 | 10 | 30 × 3 μg/kg/day | 90 | 0.090 mg |
| Dog | 25 | N/A | Initial: 25 × 2 μg/kg/day | 50 | 0.050 mg |
| Maintenance: 25 × 4 μg/kg/day | 100 | 0.100 mg |
Levothyroxine Dosage Chart by Weight
| Weight (kg) | Adult Dose (μg/day) | Elderly/Cardiac Dose (μg/day) |
|---|---|---|
| 50 | 80 – 90 | 45 – 55 |
| 60 | 96 – 108 | 54 – 66 |
| 70 | 112 – 126 | 63 – 77 |
| 80 | 128 – 144 | 72 – 88 |
| 90 | 144 – 162 | 81 – 99 |
| 100 | 160 – 180 | 90 – 110 |
Levothyroxine Dosage for Dogs by Weight Chart
| Dog Weight (kg) | Initial Dose (μg/day) | Maintenance Dose (μg/day) |
|---|---|---|
| 5 | 10 – 15 | 20 – 30 |
| 10 | 20 – 30 | 40 – 60 |
| 20 | 40 – 60 | 80 – 120 |
| 30 | 60 – 90 | 120 – 180 |
| 40 | 80 – 120 | 160 – 240 |
Levothyroxine Dosage Formula
The formula for calculating the levothyroxine dose is:
Dose (μg/day) = Weight (kg) × Dosage factor (μg/kg/day)The dosage factor varies depending on the patient’s age, severity of hypothyroidism, and other clinical factors. Common dosage factors include:
- Adults under 65: 1.6 – 1.8 μg/kg/day
- Adults over 65 or with cardiac issues: 0.9 – 1.1 μg/kg/day
- Children: 2 – 4 μg/kg/day
Example calculations:
- For a 50-year-old adult weighing 80 kg: Dose = 80 kg × 1.7 μg/kg/day = 136 μg/day
- For a 70-year-old adult weighing 65 kg: Dose = 65 kg × 1.0 μg/kg/day = 65 μg/day
Is 100 mcg of levothyroxine a high dose?
For a young, otherwise healthy adult weighing around 60-70 kg, 100 mcg would be a typical maintenance dose.
A dose of 100 mcg (micrograms) of levothyroxine is considered a moderate dose for most adults.
Whether it’s high or not depends on individual factors such as weight, age, and severity of hypothyroidism.
For elderly patients or those with heart conditions, this dose might be considered high, necessitating lower doses.
What is hypothyroidism?
Hypothyroidism is a condition marked by an underactive thyroid gland that fails to produce sufficient thyroid hormones. These hormones are crucial for:
- Regulating metabolism
- Controlling heart rate
- Managing body temperature
- Influencing brain development
Symptoms of hypothyroidism include:
- Fatigue
- Weight gain
- Cold sensitivity
- Dry skin
- Depression
- Constipation
- Muscle weakness
Levothyroxine is the standard treatment for hypothyroidism, replacing the missing thyroid hormones and helping to alleviate these symptoms.
References:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6822824/
- https://medlineplus.gov/druginfo/meds/a682461.html
- https://pubmed.ncbi.nlm.nih.gov/9770713/
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