Levothyroxine titration follows a straightforward pattern: start at a dose based on your body weight, check your TSH level every 6 weeks, and adjust by small increments until your levels fall within the normal range of 0.4 to 4.0 mIU/L. The process typically takes a few months, though it can stretch longer depending on your starting point and how your body responds.
How Starting Doses Are Calculated
For most adults under 60 with no heart problems, the standard starting dose is 1.6 mcg per kilogram of body weight per day, based on ideal (not actual) body weight. So a person whose ideal weight is around 70 kg would start at roughly 112 mcg daily. In practice, this gets rounded to the nearest available tablet size.
That weight-based calculation works well for people at a healthy weight, but it can overshoot for those who are overweight or obese. A BMI above 26 means the formula may need to be adjusted downward, since thyroid hormone dosing tracks more closely with lean body mass than total weight. Your prescriber will often start conservatively and work upward rather than risk overreplacement from the beginning.
For people with subclinical hypothyroidism (a mildly elevated TSH with no obvious symptoms), starting doses are typically lower, since the thyroid is still producing some hormone on its own.
The Adjustment Process
Once you’re on a starting dose, the next step is a blood test to check your TSH. Wait at least 6 weeks after starting or changing a dose before testing. TSH levels take that long to stabilize, and testing too early gives misleading results.
If your TSH is still above the target range, your dose goes up by 12.5 to 25 mcg. If it’s below the range, it comes down by the same increment. Then you wait another 6 weeks and test again. This cycle repeats until your TSH lands consistently in the 0.4 to 4.0 range and your symptoms have improved.
For people with severe, longstanding hypothyroidism, the increments and timing are even more cautious. Starting doses as low as 12.5 to 25 mcg per day are common, with adjustments every 2 to 4 weeks. The goal is to bring the body back up to normal thyroid function gradually, avoiding a sudden metabolic shift.
Once your TSH is stable, follow-up testing typically shifts to every 3 months for a while, then eventually to once or twice a year.
Why Consistent Absorption Matters
Titration only works if you’re absorbing the same amount of medication each time your blood is drawn. Inconsistent absorption is one of the most common reasons people seem to need repeated dose changes when the real problem is how they’re taking the pill.
Take levothyroxine in the morning on an empty stomach, at least 30 to 60 minutes before eating. Food significantly reduces absorption, and the recommendation is to wait a full 60 minutes before your first meal for best results. If you use the liquid form, the window is shorter (15 minutes before eating), since liquids absorb more quickly.
A long list of common medications and supplements interfere with levothyroxine by binding to it in your gut and preventing absorption. Calcium supplements, iron, antacids, cholesterol-lowering resins, acid reflux medications like omeprazole and lansoprazole, and phosphate binders all fall into this category. The rule is simple: take any of these at least 4 hours before or after your levothyroxine. If you’ve been taking calcium with breakfast right after your thyroid pill, that alone could explain why your TSH isn’t budging.
Titration for Older Adults and Heart Patients
If you’re over 65 or have any history of heart disease, titration starts lower and moves slower. Thyroid hormone increases your heart rate and metabolic demand, and a dose that’s safe for a healthy 35-year-old can trigger chest pain, palpitations, or dangerous heart rhythms in someone with narrowed coronary arteries or an aging heart.
Most clinicians in this group start with very low doses and uptitrate cautiously, even when cardiac problems haven’t been formally diagnosed, simply because the risk of an undetected issue is higher with age. In some cases, people with known cardiac conditions begin levothyroxine in a hospital setting where heart rhythm can be monitored. A cardiology consultation before starting is common, and the final target TSH may be set a bit higher than in younger patients to avoid pushing the heart too hard.
Adjustments During Pregnancy
Pregnancy dramatically increases your body’s need for thyroid hormone, and the timeline is urgent. If you’re already on levothyroxine and become pregnant, the American Thyroid Association recommends increasing your dose by 20% to 30% as soon as you get a positive test, before you even see your doctor. A practical way to do this: take two extra doses per week on top of your normal daily dose, which works out to roughly a 29% increase.
After that initial bump, TSH should be checked every 4 weeks throughout pregnancy, with further adjustments of 12.5 to 25 mcg as needed to keep TSH within the trimester-specific target range (which shifts as pregnancy progresses). After delivery, most people return to their pre-pregnancy dose.
Signs Your Dose Is Too High
Overtitration is not just uncomfortable. It carries real health risks. If your TSH drops below the normal range, you’re effectively in a state of hyperthyroidism, even though the excess hormone is coming from a pill rather than your thyroid gland.
The symptoms to watch for include anxiety, insomnia, tremor or shakiness, a racing or irregular heartbeat, excessive sweating, unexplained weight loss, and diarrhea. Some people notice muscle cramps, changes in their menstrual cycle, or a feeling of being “wired” that doesn’t match their usual baseline. These symptoms sometimes build gradually over weeks, making them easy to attribute to stress or other causes.
Long-term overreplacement is associated with bone loss and an increased risk of irregular heart rhythms, particularly atrial fibrillation. This is why the goal is always the lowest effective dose, not a dose that pushes TSH as low as possible. If you’re experiencing any of these symptoms, your next TSH test may confirm that a dose reduction is needed.
What Slows Down the Process
Several things can make titration take longer than expected. Weight changes alter your dose requirements. Starting or stopping medications that affect absorption (like a new acid reflux drug or iron supplement) can shift your levels. Switching between brand-name and generic levothyroxine, or between different generic manufacturers, can introduce small variations in potency that show up on your next blood test.
Inconsistent timing matters too. If you sometimes take your pill with food and sometimes without, or if you skip doses and double up, your TSH results won’t reflect a true steady state. The cleaner your routine, the faster you’ll land on the right dose and the fewer unnecessary adjustments you’ll go through.