How-to · Tablet strengths · Updated October 2, 2026
How many mcg is 0.1 mg of levothyroxine?
Direct answer
0.1 mg = 100 mcg. Multiply milligrams by 1,000. A yellow 100 mcg tablet and a 0.1 mg tablet are the same dose. 0.025 mg is 25 mcg, which is lower than 88 mcg (0.088 mg). 0.25 mg is 250 mcg, which is much higher.
U.S. tablet chart
| mcg | mg | Typical color |
|---|---|---|
| 25 | 0.025 | Orange |
| 50 | 0.05 | White |
| 75 | 0.075 | Violet |
| 88 | 0.088 | Olive |
| 100 | 0.1 | Yellow |
| 112 | 0.112 | Rose |
| 125 | 0.125 | Brown (gray for some generics) |
| 137 | 0.137 | Turquoise |
| 150 | 0.15 | Blue |
| 175 | 0.175 | Lilac |
| 200 | 0.2 | Pink |
| 300 | 0.3 | Green |
Colors follow common Synthroid tablets. Generics can use different colors, so match the mcg printed on the bottle. 100 mcg is 0.1 mg. 112 mcg is 0.112 mg. 125 mcg is 0.125 mg.
Starting dose by weight
Full replacement is about 1.6 mcg per kg per day (about 0.73 mcg per pound). A 175 lb (79.4 kg) adult is about 127 mcg, so 125 mcg is the nearest common tablet.
| Weight | 1.6 mcg/kg | Nearest tablet |
|---|---|---|
| 100 lb (45.4 kg) | 73 mcg | 75 mcg |
| 120 lb (54.4 kg) | 87 mcg | 88 mcg |
| 140 lb (63.5 kg) | 102 mcg | 100 mcg |
| 160 lb (72.6 kg) | 116 mcg | 112 mcg |
| 175 lb (79.4 kg) | 127 mcg | 125 mcg |
| 200 lb (90.7 kg) | 145 mcg | 150 mcg |
| 225 lb (102.1 kg) | 163 mcg | 175 mcg |
| 250 lb (113.4 kg) | 181 mcg | 175 mcg |
Who starts at the full weight dose
- Adult under 50–60, no heart disease, TSH markedly high: Full dose ≈ 1.6 mcg/kg/day (0.73 mcg/lb).
- Mild hypothyroidism (TSH ≤ 10): 25–50 mcg/day.
- Coronary artery disease: 12.5–25 mcg/day, slow increases.
- Older adults or atrial-fibrillation risk: Below 1.6 mcg/kg; titrate every 6–8 weeks.
- New overt hypothyroidism in pregnancy (TSH ≥ 10): 1.6 mcg/kg/day, TSH every 4 weeks.
Limits
- The weight formula is a full-replacement reference, not an automatic starting dose for a mildly high TSH.
- Changing from 100 mcg to 112 mcg is the smaller step; 125 mcg is the larger one.
- Dose changes still follow TSH and a clinician. Unit conversion only tells you which tablet you already have.
Use the calculator
What to do with the lab: how to adjust levothyroxine based on TSH. Enter TSH and the current mcg dose in the TSH dose calculator.