Hypothyroidism is treated with a daily synthetic thyroid hormone pill that replaces what your thyroid gland can no longer produce on its own. For most people, this single medication normalizes hormone levels within weeks and relieves symptoms over the following months. The treatment is lifelong in most cases, but once you find the right dose, it’s straightforward to maintain.
The Standard Medication
Levothyroxine, a synthetic version of the T4 hormone your thyroid naturally makes, is the universal first-line treatment. It works by mimicking your body’s own hormone production, and your cells convert it into the active form (T3) just as they would with natural thyroid hormones. The American Thyroid Association recommends it as the treatment of choice, including during pregnancy.
Your starting dose is calculated based on your body weight, typically 1.6 to 1.8 micrograms per kilogram of body weight per day for overt hypothyroidism. So a person weighing 70 kg (about 154 pounds) might start on roughly 112 to 126 micrograms daily. In practice, your doctor may begin with a lower dose and increase gradually, especially if you’re older or have heart concerns.
When Mild Cases Need Treatment
Subclinical hypothyroidism, where your TSH is elevated but your thyroid hormone levels are still technically normal, is a gray area. Treatment is generally recommended when TSH rises above 10 mU/L, because at that level the risk of cholesterol problems, cardiovascular events, and worsening symptoms climbs significantly.
Below that threshold, the decision depends on your individual picture. Treatment may make sense if you have thyroid antibodies (a sign of autoimmune thyroid disease), elevated cholesterol, an enlarged thyroid gland, fertility problems, or symptoms like fatigue and weight gain that align with hypothyroidism. If none of those apply and your TSH is only mildly elevated, monitoring without medication is reasonable.
How to Take It for Best Absorption
Levothyroxine is notoriously sensitive to what else is in your stomach. Taking it correctly can make the difference between a dose that works and one that doesn’t fully absorb. The basic rule: take it on an empty stomach, then wait at least 30 to 60 minutes before eating anything.
Specific foods and supplements interfere with absorption at different time windows:
- Coffee: wait at least 1 hour after taking your pill
- High-fiber foods and soy products: wait at least 1 hour
- Calcium supplements: wait 2 to 4 hours
- Iron supplements: wait 2 to 4 hours (some evidence suggests interference even at 4 to 6 hours)
- Chromium supplements: wait 3 to 4 hours
Most people find it simplest to take levothyroxine first thing in the morning with a glass of water, then go about their routine before eating breakfast. If mornings don’t work, taking it at bedtime on an empty stomach is another option, as long as you’ve waited a few hours after your last meal.
Monitoring and Dose Adjustments
After starting medication or changing your dose, your body needs about six weeks to reach a steady state because levothyroxine has a half-life of roughly one week. Your TSH should be rechecked at that six-week mark. Adjusting the dose before then doesn’t give an accurate picture of where your levels have settled.
The goal of treatment is to bring your TSH and free T4 into normal range while relieving your symptoms. Once your levels are stable, testing typically shifts to every 6 to 12 months. Your dose may need tweaking over time due to weight changes, aging, new medications, or shifts in absorption.
Risks of Taking Too Much
More is not better with thyroid hormone replacement. If your dose pushes your TSH too low, you effectively become hyperthyroid, which carries its own set of problems. Short-term, you may notice anxiety, a racing heart, trouble sleeping, and unintentional weight loss.
Over the long term, chronic over-replacement raises the risk of abnormal heart rhythms (particularly atrial fibrillation), chest pain, and bone loss that can progress to osteoporosis. This is why regular monitoring matters. Even when you feel fine, keeping your levels in range protects your heart and bones over years and decades.
Combination Therapy With T3
Some people on standard levothyroxine therapy continue to feel fatigued, foggy, or generally unwell despite normal blood results. This has led to interest in adding a synthetic T3 hormone alongside the standard T4. However, 14 clinical trials have not shown a consistent benefit of combination therapy over levothyroxine alone.
European guidelines from 2013 suggest considering combination therapy only after other possible causes of persistent symptoms have been ruled out, such as depression, sleep disorders, iron deficiency, or other conditions that mimic thyroid symptoms. If combination therapy is tried, the patient should already be taking at least 1.2 micrograms per kilogram per day of levothyroxine. People who are pregnant, have unstable heart disease, or have uncontrolled psychiatric conditions are not candidates. It remains an area where doctors disagree, and the evidence is still considered inconclusive.
Pregnancy and Hypothyroidism
If you become pregnant while taking levothyroxine, your dose will likely need to increase quickly. The American Thyroid Association recommends raising your dose by 20 to 30 percent as soon as pregnancy is confirmed, because thyroid hormone demands rise sharply in the first trimester. Waiting for a blood test result before adjusting can leave you under-treated during a critical window for fetal brain development. Your levels will be monitored closely throughout pregnancy, with the dose typically returning to pre-pregnancy levels after delivery.
Nutrients That Support Thyroid Function
Two micronutrients play direct roles in thyroid hormone production and are worth paying attention to, though neither replaces medication.
Selenium is essential for converting T4 into active T3 and for protecting the thyroid gland from oxidative damage during hormone production. For people with autoimmune thyroiditis (Hashimoto’s), selenium supplementation at 200 micrograms per day has been shown to reduce thyroid antibody levels by about 40 percent over three months, compared to roughly 10 percent in placebo groups. It’s also been linked to improved quality of life and better thyroid appearance on ultrasound. However, exceeding 400 micrograms per day risks toxicity, with symptoms including nausea, hair loss, brittle nails, and nerve damage. High selenium intake in people who aren’t deficient may also worsen blood sugar control.
Iodine is the raw material your thyroid uses to make hormones. In most developed countries, iodized salt provides enough. Supplementing with extra iodine when you’re already getting adequate amounts can actually worsen thyroid problems, so iodine supplements should only be taken if a deficiency has been confirmed. The best approach for most people is simply to eat a varied diet that includes seafood, dairy, and iodized salt.