Levothyroxine is the most common medicine for hypothyroidism. It replaces the missing thyroid hormone (T4) so you feel less tired, your metabolism steadies, and your lab numbers improve. People use it long-term, often for life, so learning the basics makes a big difference in how well it works.
Take levothyroxine on an empty stomach, 30–60 minutes before breakfast, or at bedtime at least 3 hours after your last meal. Consistency matters more than exact timing — pick a routine and stick to it. Swallow tablets whole with a glass of water. If you miss a dose and remember the same day, take it; if it’s close to the next dose, skip it and continue your schedule.
Start doses vary: young, healthy adults often begin with 50–100 mcg daily; older adults or people with heart disease start lower (12.5–25 mcg) and rise slowly. Your doctor adjusts the dose based on symptoms and TSH blood tests. Don’t change brands or formulations without checking with your prescriber — different formulations can absorb differently.
Expect a follow-up TSH test about 6–8 weeks after any dose change. That’s how clinicians know if your dose is right. Signs of under-treatment include ongoing fatigue, cold intolerance, and weight gain. Signs of too much levothyroxine are rapid heart rate, feeling jittery, trouble sleeping, and unexplained weight loss.
Important drug and food interactions: calcium, iron, magnesium, antacids, soy, and high-fiber meals can cut absorption. Space these supplements or foods at least 4 hours away from your levothyroxine. Certain meds — like some cholesterol drugs, anticonvulsants, and proton-pump inhibitors — can change how much thyroid hormone your body gets. Tell your doctor about every prescription and OTC drug you take.
Special situations: pregnancy usually requires a higher levothyroxine dose; pregnant people need close monitoring. Older adults and those with heart disease need gentler dose increases because excess thyroid hormone can trigger heart rhythm problems or bone loss over time.
When to call your doctor: new chest pain, racing heart, sudden weight changes, severe tremor, or if you can’t keep the drug down. Also call if you switch pharmacies or start a new supplement.
Quick checklist: take levothyroxine the same way each day; avoid calcium/iron within 4 hours; get TSH checked 6–8 weeks after changes; tell your provider about pregnancy or heart disease. If you buy medication online, use a reputable source and follow your country’s prescription rules. Simple routines and proper monitoring keep levothyroxine working for you.
