Many people assume thyroid replacement is simple — one pill and you're fixed. That's not always true. T4 replacement (usually levothyroxine) replaces the hormone your thyroid makes. It treats hypothyroidism, after thyroid surgery, or when radioactive iodine destroys the gland.
How it works matters. Levothyroxine is a stable form of T4. Your body converts T4 to the active T3 inside tissues. Doctors track TSH and sometimes free T4 to find the right dose. The goal: normal TSH and feeling like yourself again.
Take your T4 once a day on an empty stomach. I recommend 30–60 minutes before breakfast. Coffee, calcium, iron, antacids, and some supplements block absorption. If you must take those, leave at least four hours between them and your thyroid pill.
Keep the routine the same. If you switch brands or generics, tell your doctor and recheck TSH in 6–8 weeks. Even small changes in formulation can change how the drug works for you.
If you forget a dose, take it as soon as you remember that day. Don’t double up the next day. If you miss doses often, set an alarm or use a pillbox.
After starting or changing dose expect a blood test in 6–8 weeks. Once stable, testing every 6–12 months is common unless symptoms change. Pregnant people need higher doses and closer checks because pregnancy raises thyroid needs.
Too much T4 causes symptoms like fast heart rate, tremor, and bone loss. Older adults and people with heart disease need lower starting doses. Too little leaves you tired, cold, and slow thinking.
Some drugs interact: common ones are amiodarone, warfarin, and estrogen. Antibiotics or weight-loss drugs can also affect thyroid levels. Always tell any clinician you take levothyroxine — it matters for other prescriptions and procedures.
If you use T3-containing supplements or desiccated thyroid, discuss pros and cons with your doctor. Some people feel better on combination therapy, but evidence is mixed and dosing is trickier. Never adjust doses on your own based on how you feel without blood tests.
Expect weight changes to be slow. Many people blame thyroid for every pound, but once hormone levels are right, weight usually stabilizes. Focus on steady habits: protein at meals, regular walks, and sleep. If you have persistent hair loss, dry skin, or mood changes despite normal labs, ask for a full panel — some doctors check free T3, reverse T3, and thyroid antibodies to look for autoimmune thyroiditis. When you travel, carry a doctor's note for medication and keep pills in your carry-on. If you get sick or start a new medicine, recheck your TSH—illness and new drugs can change thyroid needs quickly.
Ask questions early.
Finally, store your pills in a cool, dry place away from sunlight. Keep track of refill changes and keep your medical team updated on other medicines and supplements you use. Small habits — timing, consistency, and follow-up tests — make the biggest difference with T4 replacement treatment.
