The standard treatment for hypothyroidism is a daily pill of levothyroxine, a synthetic version of the hormone your thyroid can no longer make enough of. It’s taken once a day on an empty stomach, and for most people it eliminates symptoms entirely once the dose is dialed in. Treatment is typically lifelong, but the routine becomes simple once you and your doctor find the right dose.
How Levothyroxine Works
Your thyroid gland normally produces a hormone called T4, which your body converts into the active form, T3. These hormones regulate your metabolism, energy levels, body temperature, heart rate, and dozens of other functions. When your thyroid underperforms, levothyroxine replaces the missing T4 directly, restoring hormone levels to their normal range.
Levothyroxine is sold under several brand names, including Synthroid and Levo-T, and comes in tablets, capsules, and liquid form. The American Thyroid Association recommends it as the standard of care for hypothyroidism because it can be manufactured with precise, consistent dosing. Your body is extremely sensitive to small changes in thyroid hormone levels, so that consistency matters. A tiny excess can cause side effects like a racing heart and anxiety, while a slight shortage leaves you symptomatic.
Finding the Right Dose
Your starting dose is calculated based on your body weight, typically around 1.6 micrograms per kilogram of body weight per day. For a 150-pound person, that works out to roughly 109 micrograms daily, though your doctor will round to the nearest available tablet size. Older adults and people with heart conditions usually start on a lower dose and increase gradually to avoid stressing the cardiovascular system.
After starting treatment, your doctor will check your blood levels (specifically TSH, or thyroid-stimulating hormone) about six to eight weeks later. TSH is the brain’s signal telling the thyroid to produce more hormone. When your replacement dose is correct, TSH drops back into the normal range. Expect a few rounds of blood work and dose adjustments over the first several months before things stabilize. Once your levels are steady, most people get tested once or twice a year.
How to Take It for Best Absorption
Levothyroxine absorption is highest when your stomach is empty. The standard recommendation is to take it first thing in the morning and wait at least 60 minutes before eating. Coffee, including espresso, and high-fiber foods can interfere with absorption if consumed too soon after the pill.
Several common supplements and medications also block absorption. Calcium, iron, aluminum-containing antacids, and proton-pump inhibitors (used for acid reflux) are among the most frequent offenders. If you take any of these, space them at least four hours apart from your levothyroxine. This single habit, consistent timing on an empty stomach, is one of the most important things you can do to keep your treatment working properly.
When Symptoms Don’t Fully Resolve
Most people feel significantly better on levothyroxine alone, but a small proportion continue to have symptoms like fatigue, brain fog, or low mood even after blood tests show their TSH is in the normal range. When that happens, the first step is ruling out other causes: sleep disorders, iron deficiency, depression, or vitamin B12 deficiency can all mimic lingering hypothyroid symptoms.
If no other explanation is found and symptoms are severe enough to affect daily life, some endocrinologists will consider a three-month trial of adding a synthetic T3 medication (liothyronine) alongside the standard T4. The British Thyroid Association notes this is appropriate only in rare cases, after thorough evaluation. If the trial doesn’t improve symptoms, the T3 is discontinued. Combination therapy remains controversial and is not part of routine treatment.
Desiccated Thyroid Extract
Before synthetic levothyroxine existed, hypothyroidism was treated with dried, ground thyroid glands from pigs, known as desiccated thyroid extract (DTE). Brands like Armour Thyroid and NP Thyroid still exist, and some patients prefer them because they contain both T4 and T3. However, the FDA has flagged significant quality concerns: because DTE is derived from animal tissue, the hormone levels can vary between pills even within the same batch. This inconsistency has led to multiple voluntary drug recalls and supply disruptions.
DTE products are not FDA-approved through the standard rigorous evaluation process that synthetic levothyroxine undergoes. Given the body’s sensitivity to even tiny fluctuations in thyroid hormone, most major medical organizations recommend synthetic levothyroxine over DTE for reliable, predictable dosing.
Subclinical Hypothyroidism
Not everyone with an underperforming thyroid needs medication right away. Subclinical hypothyroidism means your TSH is mildly elevated but your actual thyroid hormone levels are still in the normal range. You may have no symptoms at all, or only vague ones.
Treatment decisions depend on how high TSH climbs. At levels above 10 mIU/L, the evidence supports starting levothyroxine. Between 5 and 10 mIU/L, treatment is generally recommended if you have noticeable symptoms, elevated cholesterol, or are a younger adult at higher cardiovascular risk. Below that range, many doctors simply monitor with repeat blood work every six to twelve months, since mild cases sometimes resolve on their own.
Treatment During Pregnancy
Pregnancy increases the body’s demand for thyroid hormone substantially. Women already on levothyroxine are typically advised to increase their dose by 20 to 30 percent as soon as pregnancy is confirmed. A practical way to do this is to take two extra doses per week (for example, doubling up on Saturday and Sunday) until your doctor can recheck your levels and fine-tune the adjustment.
For women not previously diagnosed, the threshold for starting treatment is lower during pregnancy. The American Thyroid Association recommends levothyroxine if TSH exceeds 2.5 mIU/L, particularly when thyroid antibodies are present. Untreated hypothyroidism during pregnancy raises the risk of complications for both mother and baby, so thyroid levels are monitored more frequently throughout all three trimesters.
What to Expect Over Time
Once your dose is stable, taking levothyroxine becomes routine, much like a daily vitamin. Most people notice improvements in energy, mood, and mental clarity within the first few weeks, though full symptom relief can take two to three months as your body adjusts. Weight that crept on due to a sluggish metabolism often stabilizes, though levothyroxine alone rarely causes dramatic weight loss.
Your dose may need adjusting at certain points in life: during pregnancy, after significant weight changes, as you age, or if you start or stop medications that affect absorption. Annual or biannual blood work keeps everything on track. For the vast majority of people, levothyroxine is safe, effective, and well-tolerated for decades.