How-to · ATA 2014 steps · Educational only · Updated October 2, 2026
How do you adjust levothyroxine dose based on TSH?
Direct answer
TSH moves opposite the dose. TSH above the goal: raise levothyroxine 12.5–25 mcg. TSH below the goal: lower it 12.5–25 mcg. For most adults the goal is about 0.4–4.0 mIU/L. TSH 5.5 on 100 mcg steps to 112 mcg. Recheck in 6–8 weeks. This is not a prescription.
What a TSH result usually means on 100 mcg
| TSH (mIU/L) | Meaning | Example on 100 mcg |
|---|---|---|
| Below 0.1 | Overtreated (unless cancer suppression) | 100 → 75 mcg |
| 0.1–0.39 | Slightly overtreated | 100 → 88 mcg |
| 0.4–4.0 | On target | 100 → 100 mcg |
| 4.1–6.9 | Slightly undertreated | 100 → 112 mcg |
| 7–10 | Undertreated | 100 → 125 mcg |
| Above 10 | Clearly undertreated — check adherence and absorption | 100 → 125 mcg |
Standard adult goal (ATA 2014). Thyroid-cancer suppression is a different target and is set by the treating team.
Worked dose changes
- TSH 5.5 on 100 mcg: 100 → 112 mcg (+12 mcg). One 112 mcg (0.112 mg) tablet.
- TSH 8.5 on 75 mcg: 75 → 100 mcg. A larger step is used when TSH is well above goal.
- TSH 0.25 on 100 mcg: 100 → 88 mcg.
- TSH 0.05 on 150 mcg: 150 → 125 mcg.
- Age 70–80+, TSH 5.2 on 75 mcg: stays at 75 mcg because a TSH up to about 6 can be the goal.
- Pregnancy, TSH 3.4 on 100 mcg: 100 → 112 mcg toward a goal below 2.5. If pregnancy was just confirmed, two extra tablets a week (9 instead of 7) averages about 128.6 mcg/day before the next lab.
When to recheck
- After any dose change (adults): 6–8 weeks (ATA: 4–6). Levothyroxine half-life is about 7 days; TSH takes ~6 weeks to settle.
- Heart disease or AF risk: Titrate every 6–8 weeks. Slower increases avoid heart strain.
- Pregnancy: Every 4 weeks to mid-pregnancy, then ~30 weeks. Needs rise by 25–50% in many women.
- After delivery: Return to pre-pregnancy dose; TSH at ~6 weeks. Postpartum needs return to baseline.
- Stable dose: Every 6–12 months. Routine monitoring.
Limits
- A high TSH is often missed tablets, food, coffee, calcium, or iron — not only a dose that is slightly low.
- Central (pituitary) hypothyroidism is dosed by free T4, not TSH.
- Do not change a cancer-suppression dose, a pregnancy dose, or a heart-disease dose from this page alone.
Use the calculator
Tablet units: how many mcg is 0.1 mg of levothyroxine? Enter your TSH in the TSH dose calculator.