One small pill can change your energy, weight and mood. That’s levothyroxine — the most common treatment for an underactive thyroid (hypothyroidism). It replaces the missing thyroid hormone and usually needs daily, steady use. Want to avoid guesswork and feel more in control? Read on for clear, practical tips doctors actually give patients.
Take levothyroxine on an empty stomach, first thing in the morning. Wait 30–60 minutes before eating or drinking coffee. Why? Food and drinks cut absorption and can make doses less effective.
If you take calcium, iron or antacids, space them at least 4 hours away from your thyroid pill. Supplements with magnesium, aluminium or bile-acid binders (like cholestyramine) also interfere. If you drink a lot of soy milk or eat very high-fiber meals, try to separate those from your dose too.
Typical adult replacement often lands around 75–125 mcg daily, but it’s not one-size-fits-all. Older adults or people with heart disease often start at 12.5–25 mcg and increase slowly. Another common rule: full replacement is roughly 1.6 mcg per kg of body weight, but your doctor will tailor the dose.
Missed a dose? Take it as soon as you remember the same day. If it’s almost time for your next dose, skip the missed one — don’t double up.
Too much drug feels like having an overactive thyroid: racing heart, anxiety, sweating, trouble sleeping, or unexplained weight loss. Too little looks like low thyroid: tiredness, weight gain, cold sensitivity, and slow thinking. If you notice those signs, talk to your clinician — don’t self-adjust the dose.
Some medicines change how levothyroxine works. Enzyme inducers like rifampin, phenytoin or carbamazepine can lower thyroid levels. Estrogen therapy, pregnancy or starting/stopping certain antidepressants may raise your needs. Also, levothyroxine can increase the effect of blood thinners like warfarin — your blood clotting tests may need checking.
After any dose change, plan a blood test for TSH about 6–8 weeks later. Once stable, most people recheck every 6–12 months or sooner if symptoms change. If you become pregnant, tell your doctor — many people need higher doses and more frequent monitoring.
Keep levothyroxine at room temperature, away from humidity and direct sunlight. Try to stick with the same brand or generic if possible — switching brands can change absorption slightly. If you must switch, ask for a follow-up TSH check.
Bottom line: consistent timing, awareness of interactions, and regular blood tests make levothyroxine work well. If anything feels off, reach out to your healthcare provider — small changes can make a big difference.
