Thyroid Medications
Your thyroid controls your metabolism, energy, and mood. If it's not working right, the right medication makes a huge difference. Here's what you need to know.
Thyroid medications replace the hormones your thyroid isn't producing enough of. Levothyroxine (T4) is the standard first-line treatment. Some people do better adding T3 or using natural desiccated thyroid (NDT). The right choice depends on your labs and how you feel.
This guide is for you if: You've been diagnosed with hypothyroidism, want to understand the different thyroid medications available, or feel your current medication isn't working well enough.
See the evidenceTypes of thyroid medication
- Levothyroxine (T4) — Synthetic T4, the standard treatment. Your body converts it to active T3 as needed. Brands: Thyronorm, Eltroxin, Thyrox (India).
- Liothyronine (T3) — Synthetic T3, the active thyroid hormone. Fast-acting, short half-life. Used when T4-to-T3 conversion is poor.
- Natural desiccated thyroid (NDT) — Derived from pig thyroid, contains both T4 and T3 in a fixed ratio. Brands: Armour Thyroid, NP Thyroid (limited availability in India).
- Combination T4 + T3 — Custom ratio of levothyroxine + liothyronine, often prescribed by endocrinologists when T4 alone isn't optimal.
Comparison
| Levothyroxine (T4) | Liothyronine (T3) | NDT | |
|---|---|---|---|
| What it provides | T4 only | T3 only | T4 + T3 (4:1 ratio) |
| Half-life | ~7 days | ~1 day | Mixed |
| Dosing | Once daily | 2–3x daily | Once or twice daily |
| India availability | Widely available | Available (limited brands) | Difficult to source |
| Cost | ₹50–200/month | ₹200–600/month | ₹800–2,000/month (imported) |
Optimising your thyroid medication
Empty stomach, first thing in the morning. Wait at least 30–60 minutes before eating, coffee, or other supplements.
Iron, calcium, magnesium, and antacids all reduce absorption — space them at least 4 hours apart. Consistency matters: same time, same conditions, every day.
Signs your dose may need adjusting:
- Still fatigued, gaining weight, or feeling cold despite "normal" TSH → may need T3 added or dose increased
- Anxiety, heart palpitations, weight loss, insomnia → may be over-medicated
- TSH in range but Free T3 is low → poor T4-to-T3 conversion (consider adding T3)
Many doctors only check TSH. For proper thyroid management, you need TSH, Free T4, Free T3, and thyroid antibodies (TPO, TgAb). Free T3 is the active hormone — if it's low, you may feel hypothyroid even with a "normal" TSH.
Track your thyroid properly
eterni tracks TSH, Free T3, Free T4, and antibodies over time — so you can see trends, not just single snapshots.
Get early accessFrequently Asked Questions
Why do I still feel tired on levothyroxine?
Several possibilities: your dose is too low (TSH is still above optimal), you're not converting T4 to T3 well (check Free T3), you have nutrient deficiencies that impair thyroid function (iron, selenium, zinc, vitamin D), or you have Hashimoto's with ongoing inflammation. Don't accept 'your labs are normal' if you still feel terrible — push for a full panel.
Is natural thyroid (NDT) better than levothyroxine?
Not inherently — but some patients feel better on NDT because it provides both T4 and T3. The T4:T3 ratio in NDT (~4:1) is different from the human thyroid (~14:1), so it delivers relatively more T3. For patients who convert T4 to T3 poorly, this can be beneficial. However, NDT is harder to dose precisely and has more batch-to-batch variability.
Can supplements help my thyroid?
Selenium (200 mcg/day) can reduce thyroid antibodies in Hashimoto's and supports T4-to-T3 conversion. Zinc (15–30 mg/day) and iron (if deficient) are also important for thyroid function. Ashwagandha can raise T3/T4 in subclinical hypothyroidism but should be used cautiously with thyroid medication. Iodine is needed but most Indians get enough from iodised salt.
How often should I retest thyroid levels?
Every 6–8 weeks after any dose change (it takes this long for levels to stabilise). Once stable, every 3–6 months. Always test in the morning, before taking your thyroid medication, and at the same time of day for consistency. Include Free T3, Free T4, and TSH — not just TSH alone.
T4-to-T3 conversion and why it matters
Levothyroxine provides T4 (thyroxine), which is a prohormone — relatively inactive until converted to T3 (triiodothyronine) by deiodinase enzymes (primarily DIO1 and DIO2) in the liver, kidneys, and target tissues. T3 is approximately 4x more biologically active than T4.
Some patients are poor converters — their Free T4 is adequate on levothyroxine, but Free T3 remains low. Contributing factors include selenium deficiency (selenium is required for deiodinase function), chronic inflammation, liver dysfunction, and certain genetic polymorphisms in the DIO2 gene.
The optimal ranges debate: Many endocrinologists consider TSH 0.5–4.5 mIU/L as "normal," but functional medicine practitioners argue that optimal is TSH 0.5–2.0, Free T4 in the upper half of range, and Free T3 in the upper third. While not universally accepted, many patients report feeling better when their Free T3 is optimised, not just their TSH.
Know what's working. Know what's not.
eterni connects your lab results, supplements, and retests — so you can see the trajectory, not just a snapshot.
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