Levothyroxine Dosages: Your GoodRx Guide
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 it 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 type of thyroid hormone medication you’re taking.
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Table of contents
Levothyroxine (Levoxyl, Synthroid, Tirosint) is a lab-made form of thyroxine (T4), a thyroid hormone. It’s primarily used to treat low thyroid hormone levels (hypothyroidism). Levothyroxine helps restore your thyroid hormone levels when they’re lower than they should be.
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 you’re taking levothyroxine, 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. 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 have stabilized, 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 12 years old 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 instances 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 dose more often during your pregnancy. You’ll usually go back to your pre-pregnancy levothyroxine dosage immediately after delivery.
How does it feel to take levothyroxine? Read first-hand accounts of what it’s like to take levothyroxine.
Levothyroxine side effects: Review common and rare side effects that can happen while you’re taking levothyroxine and how to manage them.
What’s the best way to take levothyroxine? Here are some pharmacist-backed tips to help you get the most from your thyroid hormone medication.
If you’re newly diagnosed with hypothyroidism during pregnancy, you may start with a lower levothyroxine dosage (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, every 6 to 8 weeks.
Dosage for people with heart problems
Adults with heart problems should start with a lower levothyroxine dosage as well. The starting dosage will usually be around 12.5 mcg to 25 mcg daily, with slow increases every 6 to 8 weeks. This helps to avoid levothyroxine side effects, such as increased heart rate, that could be more dangerous if you have heart problems.
Infants up to 3 months old at risk for heart problems may also require a lower levothyroxine dosage and slower increases than normally recommended.
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:
Formulation | Brand Name(s) | Available doses |
Levothyroxine tablets | • 25 mcg (orange) | |
Levothyroxine capsule | • 13 mcg (green) | |
Levothyroxine oral liquid | • 13 mcg/mL (green) These are the colors of the bottle label, not the liquid itself | |
Oral liquid | 20 mcg/mL (100 mcg/5 mL) | |
Oral liquid | 30 mcg/mL (150 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 from one brand of levothyroxine to another, or from brand-name to generic versions. 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 best to 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. It’s recommended to take levothyroxine first thing in the morning, about 30 to 60 minutes before your first meal of the day.
Tirosint capsules must be swallowed whole — you shouldn’t open them. But you can crush the tablets and mix them with 1 tsp to 2 tsp of water if you have trouble swallowing pills. Make sure to drink the mixture right away, and don’t make it in advance. You shouldn’t mix crushed tablets with anything other than water.
The liquid formulation of levothyroxine is another alternative if you have trouble swallowing tablets or capsules. They may also be a better option if you can’t tolerate gluten or lactose, common ingredients in some tablets and capsules.
Other medications can also affect how much levothyroxine your body absorbs. It’s best to separate it from other medications by at least 4 hours.
Can you take levothyroxine at night?
Yes, you can take levothyroxine in the evening, at least 2 hours after your last meal or snack of the day. This may be an easier option if you take other medications in the morning or don’t like delaying your breakfast. 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 in a row, call your prescriber. They may adjust your dose for a short while to get your thyroid hormone levels back to normal. 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 many 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. GoodRx can help you save over 60% off the average retail price of the generic version.
Generic levothyroxine’s price at certain pharmacies is as low as $9.75 with a free GoodRx discount.
There are also several copay savings cards available for the various brand-name versions of levothyroxine. If eligible, these copay cards can help you save on the following:
Synthroid: Pay as little as $25 for a 30-day supply.
Unithroid: Pay as little as $3 for a 30-day supply.
Tirosint: Pay as little as $25 for a 30-day supply.
Tirosint-SOL: Pay as little as $15 for a 30-day supply, or $40 for a 90-day supply.
Thyquidity: Pay as little as $0 for your prescription.
Ermeza: Pay as little $0 for your first prescription, and then $20 per month thereafter.
If you’re uninsured or underinsured, you may be eligible for Ermeza, Tirosint, and Tirosint-Sol patient assistance programs, which offer the medication free of cost.
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 that 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
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IBSA Pharma Inc. (2023). Tirosint SOL- levothyroxine sodium solution. Tirosint SOL- levothyroxine sodium solution [package insert].
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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.
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