Key takeaways:
Levothyroxine (Levoxyl, Synthroid, Tirosint) is a synthetic form of thyroxine (T4), a thyroid hormone. It treats hypothyroidism by bringing your thyroid hormone levels into the desired range.
The initial levothyroxine dosage for adults is around 1.6 mcg per kg of body weight. But this may vary based on your age and other health conditions. Your prescriber will adjust your dose every 4 to 6 weeks based on your thyroid stimulating hormone levels and how you’re feeling.
Levothyroxine is available as several different brand-name medications. You can also find levothyroxine tablets as a lower-cost generic. GoodRx can help you save on the cost of your prescription. But be sure to check with your healthcare team first before making changes to the form of levothyroxine you’re taking.
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Levothyroxine (Levoxyl, Synthroid, Tirosint) is a lab-made form of thyroxine (T4), a thyroid hormone. It’s mainly used to treat hypothyroidism (low thyroid hormone levels). But what’s the right dose of levothyroxine?
This guide looks closer at the approved levothyroxine dosages for adults and children. Be aware that your prescriber may have you take levothyroxine differently than discussed below. If you have questions about how dose, speak with your healthcare team.
What’s the typical levothyroxine dosage for adults?
Your levothyroxine dose is based on your body weight. For adults, it’s recommended to start with a levothyroxine dosage of 1.6 mcg per kg of body weight daily. That’s around 100 mcg per day for a person who weighs 150 lbs (68 kg). Your prescriber will calculate your dose for you.
After 4 to 6 weeks, your prescriber will likely check your thyroid stimulating hormone (TSH) level. TSH levels go up when your thyroid hormone levels are too low, and come down when your thyroid levels are where they should be. Measuring your TSH is usually the best way to know how well levothyroxine is working.
Depending on your TSH level, your prescriber may make changes to your levothyroxine dosage. It’s recommended to only change the dose by 12.5 mcg to 25 mcg at a time. Once your TSH levels stabilize, you’ll likely only need it tested once every 6 to 12 months.
What’s the typical levothyroxine dosage for children?
The levothyroxine dosage for children depends on their age and body weight, as shown in the table below. Since thyroid hormone plays a key role in growth and development, children have higher starting levothyroxine dosages than adults.
Age | Starting levothyroxine daily dose |
|---|---|
0-3 months | 10-15 mcg/kg |
3-6 months | 8-10 mcg/kg |
6-12 months | 6-8 mcg/kg |
1-5 years | 5-6 mcg/kg |
6-12 years | 4-5 mcg/kg |
Older than age 12 but still going through puberty | 2-3 mcg/kg |
Finished going through puberty | 1.6 mcg/kg |
Your pediatrician will calculate your child’s dose. They’ll likely need to check your child’s TSH levels every 2 weeks or so and adjust their levothyroxine dosage as needed.
Dosing for children at risk for hyperactivity
Children at risk for hyperactivity may need a lower starting levothyroxine dosage. It’s recommended to start with 25% of the recommended dose for their age group, then slowly increase it by another 25% of the recommended dose each week.
Are there any dosage adjustments for age or medical conditions?
There are several things that can affect your levothyroxine dosage. Let’s review the most common.
Dosage during pregnancy
Pregnancy increases your body’s need for thyroid hormone. So be sure to tell your prescriber right away if you become pregnant. They’ll need to check your TSH levels and adjust your levothyroxine dose more often throughout your pregnancy. You’ll usually go back to your pre-pregnancy dose immediately after delivery.
If you’re newly diagnosed with hypothyroidism during pregnancy, you may start with a levothyroxine dosage of 1 mcg per kg of body weight, depending on your TSH level. Your prescriber will be able to determine the best dosage for your needs.
Dosage for people 65 years and older
A lower starting levothyroxine dosage is recommended for people ages 65 and over. Some manufacturers recommend a starting dosage of 12.5 mcg to 25 mcg daily. But your prescriber will determine the best starting dosage for your specific needs. It’s also best to increase the dosage slower in older adults, once every 6 to 8 weeks.
Dosage for people with heart problems
Adults living with heart problems should also start with a lower levothyroxine dosage. The starting dosage will usually be around 12.5 mcg to 25 mcg daily, with slow increases every 6 to 8 weeks. This helps avoid levothyroxine side effects, such as increased heart rate, that could be more dangerous for those with heart problems.
A lower starting levothyroxine dose and slower increases are also recommended for infants up to the age of 3 months who are at risk for heart problems.
What dosage forms does levothyroxine come in?
Levothyroxine is an oral medication taken once a day. It’s available as tablets, capsules, and several different oral liquids. The available doses for the most common forms of levothyroxine are listed below:
Levothyroxine Dosage Form | Brand Name(s) | Available doses |
|---|---|---|
Tablets | Synthroid Levoxyl Unithroid Euthyrox Levo-T | • 25 mcg (orange) • 50 mcg (white) • 75 mcg (violet) • 88 mcg (olive) • 100 mcg (yellow) • 112 mcg (rose) • 125 mcg (brown) • 137 mcg (turquoise) • 150 mcg (blue) • 175 mcg (lilac) • 200 mcg (pink) • 300 mcg (green) |
Capsule | Tirosint | • 13 mcg (green) • 25 mcg (orange) • 37.5 mcg (dark blue) • 44 mcg (red) • 50 mcg (white) • 62.5 mcg (gray) • 75 mcg (purple) • 88 mcg (olive) • 100 mcg (yellow) • 112 mcg (rose) • 125 mcg (brown) • 137 mcg (turquoise) • 150 mcg (blue) • 175 mcg (lilac) • 200 mcg (pink) |
Oral liquid | • 13 mcg/mL (green) • 25 mcg/mL (orange) • 37.5 mcg/mL (dark blue) • 44 mcg/mL (red) • 50 mcg/mL (white) • 62.5 mcg/mL (gray) • 75 mcg/mL (purple) • 88 mcg/mL (olive) • 100 mcg/mL (yellow) • 112 mcg/mL (rose) • 125 mcg/mL (brown) • 137 mcg/mL (turquoise) • 150 mcg/mL (blue) • 175 mcg/mL (lilac) • 200 mcg/mL (pink) | |
Oral liquid | • 20 mcg/mL (100 mcg/5 mL) |
Even though all of these medications contain levothyroxine, minor differences in the formulation between brands can affect your thyroid hormone levels. So it’s best not to switch between brands of levothyroxine — or from brand-name to generic versions — unless your prescriber recommends it. If your medication looks different than usual when you pick it up from the pharmacy, check with the pharmacist before taking it.
How should you take levothyroxine?
It’s recommended to take levothyroxine first thing in the morning, about 30 to 60 minutes before your first meal of the day. Other medications can affect how much levothyroxine your body absorbs. So it’s best to separate it from other medications by at least 4 hours.
You should take levothyroxine the same way every day. A change in how or when you take it can make a big difference in how you absorb the medication. If you make any changes, be sure to let your prescriber know.
If you have trouble swallowing pills, you can crush levothyroxine tablets and mix them with 1 to 2 teaspoons of water. Make sure to drink the mixture right away. Don’t make it in advance to save for later. You shouldn’t mix crushed tablets with anything other than water. Tirosint capsules must be swallowed whole — you shouldn’t open them.
Levothyroxine also comes in liquid forms if you have trouble swallowing pills. They may also be a better option if you can’t tolerate gluten or lactose, common ingredients in some tablets and capsules.
Can you take levothyroxine at night?
Yes, you can take levothyroxine in the evening. This may be an easier option if you take other medications in the morning or don’t like delaying your breakfast. But it’s best to make sure it’s at least 4 hours after any other medications and 2 hours or more after your last meal or snack of the day. The most important thing is to choose a time of day you can stick with consistently.
What happens if you miss a dose of levothyroxine?
If you miss a dose of levothyroxine, take it as soon as you remember. But if it’s almost time for your next dose, skip the missed dose and just take your next one as scheduled. Don’t take two doses at the same time to make up for a missed dose.
If you miss multiple doses of levothyroxine in a row, contact your prescriber. They may adjust your dose for a short while to get your thyroid hormone levels back on track. They can also suggest tips or medication reminder apps to help you remember to take your medication.
What should you do if you take too much levothyroxine?
If you take an extra dose of levothyroxine by mistake, it’s not likely to cause a problem. But large amounts of levothyroxine can cause sweating, tremors, and trouble sleeping. It can also cause confusion. In rare cases, shock, coma, and even death can occur.
Signs of a levothyroxine overdose can take several days to appear. So if you or a loved one takes too much levothyroxine, contact your healthcare team or call Poison Control at 1-800-222-1222, even if you don’t notice any symptoms.
If you experience seizures, chest pain, or confusion after taking too much levothyroxine, seek medical care right away.
How to save on levothyroxine
There are several ways to save on your levothyroxine medication. GoodRx can help you navigate your options, which will vary based on the type and brand of medication you take.
Save with GoodRx. You can pay as little as $4.00 for a 30-day supply of levothyroxine 100 mcg tablets at certain pharmacies with a free GoodRx discount. GoodRx also offers exclusive discounts on the cost of brand-name Levoxyl, Tirosint and Tirosint-SOL.
Save with Companion. You can access discounted prescription medications with a GoodRx Companion subscription. Over 250 medications (including some forms of levothyroxine) are available for free, with hundreds more for under $10. The program also includes benefits to help you cut your self-pay costs, such as lower prices for online care visits, discounts on dental care, and other health services.
Save with a copay savings card. If you have commercial insurance, you may be able to save on the cost of several brand-name versions of levothyroxine using a copay savings card from the manufacturer:
Synthroid: Pay as little as $25 for a 30-day supply ($39.95 without insurance).
Unithroid: Pay as little as $3 for a 30-day supply.
Tirosint: Pay as little as $25 for a 30-day supply, or $60 for a 90-day supply.
Tirosint-SOL: Pay as little as $25 for a 30-day supply, or $60 for a 90-day supply.
Thyquidity: Pay as little as $0 for your prescription.
Save with a patient assistance program. If you’re uninsured or underinsured, you may be eligible for patient assistance programs for Synthroid, Tirosint, or Tirosint-SOL, which offer these medications free of cost.
Frequently asked questions
Levothyroxine comes in doses ranging from 13 mcg to 300 mcg. So a 100 mcg dose falls somewhere in the middle. Keep in mind that your levothyroxine dosage is determined by your TSH level. Everyone responds to the medication differently. So your levothyroxine dose is specific to your needs and may not be the same as someone else’s.
It’s best to wait 4 hours after taking levothyroxine before consuming dairy products. This is because the calcium in these foods can bind to levothyroxine and prevent your body from absorbing it. If you already have an established routine that doesn’t follow this recommendation, it’s likely that your prescriber has already adjusted your levothyroxine dose to account for it. But if you make any changes to how or when you take levothyroxine, be sure to let them know.
Low thyroid hormone levels lead to symptoms such as:
Fatigue
Weight gain
Feeling cold
Dry skin
Hair loss
Constipation
Depression
If you’re taking levothyroxine and feeling symptoms of hypothyroidism, let your prescriber know. They can check your hormone levels to see if they’re where they should be. Keep in mind it can take 4 to 6 weeks for thyroid medication to improve your symptoms.
Levothyroxine comes in doses ranging from 13 mcg to 300 mcg. So a 100 mcg dose falls somewhere in the middle. Keep in mind that your levothyroxine dosage is determined by your TSH level. Everyone responds to the medication differently. So your levothyroxine dose is specific to your needs and may not be the same as someone else’s.
It’s best to wait 4 hours after taking levothyroxine before consuming dairy products. This is because the calcium in these foods can bind to levothyroxine and prevent your body from absorbing it. If you already have an established routine that doesn’t follow this recommendation, it’s likely that your prescriber has already adjusted your levothyroxine dose to account for it. But if you make any changes to how or when you take levothyroxine, be sure to let them know.
Low thyroid hormone levels lead to symptoms such as:
Fatigue
Weight gain
Feeling cold
Dry skin
Hair loss
Constipation
Depression
If you’re taking levothyroxine and feeling symptoms of hypothyroidism, let your prescriber know. They can check your hormone levels to see if they’re where they should be. Keep in mind it can take 4 to 6 weeks for thyroid medication to improve your symptoms.
The bottom line
For most adults, the starting levothyroxine (Levoxyl, Synthroid, Tirosint) dosage will be around 1.6 mcg per kg of body weight. But this can vary based on your age and other health conditions. After you start taking levothyroxine, your prescriber will likely adjust your dosage every 4 to 6 weeks based on your thyroid stimulating hormone (TSH) levels and how you feel. The levothyroxine dosage for children is based on their age and body weight.
There are several different brands of levothyroxine available, such as Levoxyl, Synthroid, and Tirosint. They’re equally effective, but you shouldn’t switch between them. Be sure to take your levothyroxine at the same time every day on an empty stomach. You can take it in the morning or in the evening, just be sure to separate it from other medications by at least 4 hours. This helps you absorb levothyroxine and keep your thyroid hormone levels stable.
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References
American Thyroid Association. (n.d.). Hypothyroidism in pregnancy.
Eghtedari, B., et al. (2023). Levothyroxine. StatPearls.
Gluvic, Z., et al. (2021). Levothyroxine treatment and the risk of cardiac arrhythmias – focus on the patient submitted to thyroid surgery. Frontiers in Endocrinology.
IBSA Pharma Inc. (2026). Tirosint SOL- levothyroxine sodium solution. Tirosint SOL- levothyroxine sodium solution [package insert].
IBSA Pharma Inc. (2026). Tirosint- levothyroxine sodium capsule [package insert].
NuCare Pharmaceuticals, Inc. (2026). Levothyroxine sodium- levothyroxine sodium tablet [package insert].
Oliva Therapeutics, LLC. (2025). Thyquidity- levothyroxine sodium solution [package insert].
Pirahanchi, Y., et al. (2023). Physiology, thyroid stimulating hormone. StatPearls.
Rajput, R., et al. (2011). Can levothyroxine be taken as evening dose? Comparative evaluation of morning versus evening dose of levothyroxine in treatment of hypothyroidism. Journal of Thyroid Research.
Razo, L. (2023). Synthroid (levothyroxine): Side effects, interactions, and overdose. Poison Control.
Segni, M., et al. (2017). Disorders of the thyroid gland in infancy, childhood and adolescence. Endotext.
