🦋 Thyroid
Thyroid Medications — Levothyroxine and Alternatives (2026)
Complete guide to thyroid medications — levothyroxine dosing, taking it correctly, side effects, and when T3 or desiccated thyroid may help. Updated January 2026.
Key Takeaways
- Levothyroxine (T4) is first-line treatment for hypothyroidism
- Take levothyroxine on an empty stomach, 30–60 minutes before food
- Many foods and medications impair levothyroxine absorption — timing is critical
- Some patients feel better on combination T4/T3 therapy — discuss with endocrinologist
- TSH should be checked 6–8 weeks after any dose change to confirm level
Levothyroxine — The Standard Treatment
Levothyroxine sodium (brand names: Eltroxin, Synthroid, Euthyrox) is synthetic thyroxine (T4) — the standard treatment for hypothyroidism (underactive thyroid). T4 is the storage hormone that is converted to active T3 (triiodothyronine) in peripheral tissues throughout the body.
30–60 min
Before food — optimal levothyroxine absorption window
6–8 weeks
Time to check TSH after any dose change
1.6 mcg/kg
Typical full replacement dose calculation
How to Take Levothyroxine Correctly
- Take on an empty stomach — ideally 30–60 minutes before breakfast or at bedtime (2 hours after last food)
- Take with water only — not tea, coffee, or milk which impair absorption
- Be consistent — same time every day
- Separate from supplements — calcium, iron, and magnesium reduce absorption by 20–40%; take at least 4 hours apart
What Impairs Levothyroxine Absorption
| Substance | Effect on Absorption | Solution |
|---|---|---|
| Calcium supplements | Reduces by 20–40% | Separate by at least 4 hours |
| Iron supplements | Reduces by 30–55% | Separate by at least 4 hours |
| Magnesium supplements | Reduces by 20% | Separate by at least 4 hours |
| Proton pump inhibitors (omeprazole) | Reduces by 15–25% | Discuss dose adjustment with GP |
| Soy products | Reduces absorption | Separate by 4 hours |
| Coffee | Impairs absorption if taken together | Take levo 30 min before first coffee |
| High-fibre diet | Mild reduction | Take consistently with or without fibre |
When T4-Only Treatment Is Insufficient
Some patients remain symptomatic (fatigue, brain fog, weight issues) despite TSH in normal range on levothyroxine. Possible reasons: poor T4-to-T3 conversion (genetic DIO2 variants), suboptimal TSH target, or individual variation. Options to discuss with endocrinologist:
- Optimise TSH target: Aim for TSH 1.0–2.0 mIU/L rather than accepting any value within the broad normal range
- Combination T4/T3 (levothyroxine + liothyronine): Some patients with DIO2 variants respond better — specialist-prescribing only
- Desiccated thyroid extract (DTE): Natural thyroid derived from porcine glands — contains both T4 and T3; some patients prefer but inconsistent T3:T4 ratios
Frequently Asked Questions
How long does levothyroxine take to work?▼
Levothyroxine begins raising T4 levels within hours, but the full clinical effect takes 4–6 weeks — because TSH falls slowly and peripheral tissue conversion to T3 takes time. Most people notice symptom improvement within 2–4 weeks. TSH should be rechecked 6–8 weeks after any dose change to confirm the level is in the optimal range.
Can I take levothyroxine at night?▼
Yes — bedtime dosing (at least 2 hours after last food) is now considered equally or even slightly more effective than morning dosing in several studies, with better absorption due to the overnight fasting period. If you prefer morning dosing, take 30–60 minutes before breakfast. Choose whichever time you can be most consistent with.
Why do I feel worse even though my TSH is 'normal'?▼
The TSH normal range (0.4–4.0 mIU/L) is broad — many patients feel best at TSH 1.0–2.0 mIU/L. If your TSH is 3.5 (normal but high), you may benefit from dose optimisation. Also consider: whether T4-to-T3 conversion is adequate (check free T3 levels), whether you are taking levothyroxine optimally (timing and interactions), and whether other conditions (iron deficiency, vitamin D deficiency, sleep apnoea) are contributing to symptoms.
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⚕️ Medical Disclaimer: For informational purposes only. Always consult a qualified healthcare professional before starting or changing any medication or treatment.
Dr
Dr. Priya Sharma, MD
WellCalc Medical Contributor
All articles reviewed by qualified healthcare professionals.