Should You Increase Synthroid Again After Only Two Weeks?
Wait 4-6 more weeks before making another dose adjustment. Two weeks is insufficient time for levothyroxine to reach steady state, and adjusting the dose now risks overshooting into iatrogenic hyperthyroidism.
Why You Must Wait
The peak therapeutic effect of levothyroxine takes 4-6 weeks to manifest 1. Your patient's current labs reflect their previous dose, not the dose increase made two weeks ago. The TSH of 22.8 mIU/L will continue to decline over the next 4-6 weeks as the new dose reaches steady state 2, 3.
- Levothyroxine has a long half-life requiring 6-8 weeks to achieve stable serum concentrations after any dose change 2, 3
- Adjusting doses more frequently than every 6-8 weeks is a critical error that leads to dose-stacking and overtreatment 2, 3
- Approximately 25% of patients on levothyroxine are unintentionally maintained on excessive doses due to premature dose adjustments 2
The Correct Monitoring Timeline
Recheck TSH and free T4 in 4-6 more weeks (6-8 weeks total from the dose increase) 2, 3, 1. This timing allows:
- Full equilibration of serum thyroid hormone levels 1
- Accurate assessment of whether the current dose is adequate 2, 3
- Prevention of iatrogenic hyperthyroidism from premature dose escalation 2
What to Expect at 6-8 Weeks
At the 6-8 week recheck, if TSH remains >10 mIU/L despite the recent increase:
- Increase levothyroxine by 12.5-25 mcg based on the patient's age and cardiac status 2, 3, 1
- Use 25 mcg increments for patients <70 years without cardiac disease 3, 1
- Use 12.5 mcg increments for patients >70 years or with cardiac disease 2, 3
- Target TSH should be 0.5-4.5 mIU/L with normal free T4 2, 3
Critical Safety Considerations
Before any future dose increase, rule out adrenal insufficiency if the patient has:
- History of autoimmune conditions (given the severe hypothyroidism, likely Hashimoto's) 2, 3
- Pituitary disease or immunotherapy exposure 2, 3
- Unexplained hypotension, hyponatremia, or hypoglycemia 2
Starting or increasing thyroid hormone before addressing adrenal insufficiency can precipitate life-threatening adrenal crisis 2, 3.
Why This TSH Level Matters
A TSH of 22.8 mIU/L represents severe primary hypothyroidism that absolutely requires treatment, but the timing of dose adjustments must be methodical:
- TSH >10 mIU/L carries ~5% annual risk of progression and cardiovascular complications 2, 3
- The severely elevated TSH confirms inadequate replacement, but patience is required for proper titration 2, 3
- Rushing dose adjustments increases risk of atrial fibrillation, osteoporosis, and cardiac complications from overtreatment 2, 3
Common Pitfall to Avoid
Do not be tempted to increase the dose now simply because the TSH is still very elevated. The current TSH reflects the old dose, not the increase made two weeks ago 2, 3. Making another adjustment now would result in dose-stacking, potentially causing the patient to swing from severe hypothyroidism to iatrogenic hyperthyroidism within weeks 2.