This article describes Synthroid oral tablet’s dosages and strengths and gives details on how to take it. You’ll also find information on cost savings and coupon options for Synthroid. If you want to know more about Synthroid oral tablet, see this overview article. It covers details about the drug’s uses and side effects, ways to save on cost, and more.
Synthroid is a brand-name medication that comes as an oral tablet. It’s available in a generic version called levothyroxine. This article describes dosages of Synthroid.
Boxed warning: Not for use to treat obesity or as a weight loss aid
Synthroid has a boxed warning about it not being used to treat obesity or as a weight loss aid. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
See the end of this article for more information about this warning.
Form and strengths of Synthroid
Synthroid oral tablet comes as follows:
- Form: tablet that you swallow
- Strengths: 25 micrograms (mcg), 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg
Dosage of Synthroid
This article describes the recommended dosages for Synthroid oral tablet. The drugmaker provides these dosages.
If your doctor prescribes this medication, you should follow the dosage they prescribe. Your doctor will determine the dosage that best meets your needs. Do not change your dosage of Synthroid oral tablet without your doctor’s recommendation.
Usual recommended dosages of Synthroid in adults
Usually, doctors start by prescribing a low dosage of Synthroid oral tablet. Then, they’ll adjust it over time until the right dosage is reached. Ultimately, your doctor will prescribe the smallest dosage of Synthroid oral tablet that gives the desired outcome.
Dosage for adults with hypothyroidism
The dosages for Synthroid oral tablet are in micrograms (mcg). Dosages depend on body weight in kilograms (kg). For reference, 1 kg is about 2.2 pounds (lb).
The table below outlines the recommended dosages of Synthroid oral tablet for hypothyroidism in adults. Dosages are shown in micrograms per kilogram of body weight per day (mcg/kg/day).
| Group | Usual starting dosage | Frequency | Dosage adjustment |
|---|---|---|---|
| adults with hypothyroidism | 1.6 mcg/kg/day | once per day | increased by 12.5–25 mcg every 4–6 weeks, until typical thyroid hormone levels are reached |
| adults at risk of atrial fibrillation (AFib) or with heart disease | less than 1.6 mcg/kg/day | once per day | increased every 6–8 weeks, until typical thyroid hormone levels are reached |
| older adults (people ages 65 years and older) | less than 1.6 mcg/kg/day | once per day | increased every 6–8 weeks, until typical thyroid hormone levels are reached |
Dosages over 200 mcg per day are not usually needed for hypothyroidism. Dosages over 300 mcg per day that aren’t working are rare and may be due to poor absorption of the drug or other factors.
Dosage for adults with thyroid cancer
The dosages of Synthroid oral tablet are in micrograms (mcg). Dosages depend on the type of thyroid cancer and the thyroid hormone level goal specific to the stage of the cancer. Dosages may also be adjusted according to other factors about the person.
Dosages of Synthroid in children
Usually, doctors start by prescribing a low dosage of Synthroid oral tablet. Then, they’ll adjust it over time until the right dosage is reached. Ultimately, the doctor will prescribe the smallest dosage of Synthroid oral tablet that gives the desired outcome.
Dosage for children with hypothyroidism
The dosages for Synthroid oral tablet are in micrograms (mcg). Dosages depend on body weight in kilograms (kg). For reference, 1 kg is about 2.2 pounds (lb). Dosage also depends on the child’s age.
The table below outlines the recommended dosages of Synthroid oral tablet for hypothyroidism in children in micrograms per kilogram of body weight per day (mcg/kg/day).
| Age | Usual starting dosage | Frequency |
|---|---|---|
| 0–3 months | 10–15 mcg/kg/day | once per day |
| 3–6 months | 8–10 mcg/kg/day | once per day |
| 6–12 months | 6–8 mcg/kg/day | once per day |
| 1–5 years | 5–6 mcg/kg/day | once per day |
| 6–12 years | 4–5 mcg/kg/day | once per day |
| older than 12 years but still growing or going through puberty | 2–3 mcg/kg/day | once per day |
| older than 12 years but no longer growing and have gone through puberty | 1.6 mcg/kg/day | once per day |
In children, the dosage may be adjusted every 2 weeks until typical thyroid hormone levels are reached. Some children, such as those at risk of heart problems, may need to start at lower dosages. Or the dosage may need to be adjusted more quickly or more slowly than in other children.
Dosage adjustments for Synthroid
Your doctor will prescribe a dosage of Synthroid oral tablet based on several factors. These include:
- the specific condition being treated and how severe it is
- your age
- your weight
- other health conditions you may have, including whether you’re pregnant
- other medications or supplements you take
- how you take the medication with regards to food
You may not see the full effect of Synthroid oral tablet for about 4–6 weeks. The dose may need to be adjusted until typical thyroid hormone levels are reached.
Missed dose of Synthroid
Talk with your doctor or pharmacist right away if you realize you forgot to take a dose of Synthroid oral tablet. They may advise you to take the missed dose. Or they may advise you to skip it and take your next dose as scheduled.
For tips on how to plan your doses of Synthroid oral tablet and avoid missing a dose, read this article. You could also try:
- downloading a reminder app on your phone
- setting an alarm
- putting a note where you’ll see it, such as on your calendar, bathroom mirror, or bedside table
Frequently asked questions
Below are answers to some commonly asked questions about Synthroid oral tablet and its dosage.
What is considered a high dose of Synthroid?
Dosages of Synthroid over 200 mcg per day are not usually needed for hypothyroidism. And dosages over 300 mcg per day are rare. In fact, the highest strength of Synthroid oral tablet available is 300 mcg. Plus, larger doses can cause serious or even life threatening side effects.
Your dose of Synthroid oral tablet can vary based on many factors, including your age, weight, and other health conditions you may have. Your doctor will adjust your dosage based on how you respond and when you reach typical thyroid hormone levels.
Some factors can affect how well you absorb Synthroid oral tablet, including whether you take it with food or other medications or supplements. For details, see the “How Synthroid is taken” section below. Missed doses can also affect how well you respond to the medication.
If you feel that your dosage of Synthroid oral tablet isn’t working well to treat your symptoms or that you need a higher dose, talk with your doctor or pharmacist. They can work with you to find out why your dosage may not be having the desired effect.
Is Synthroid taken long term?
Yes, doctors typically prescribe Synthroid oral tablet as a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take it long term.
If you have questions about how long you should take Synthroid oral tablet, talk with your doctor.
How Synthroid is taken
You’ll swallow Synthroid oral tablet once per day. The drugmaker recommends taking it on an empty stomach, about 30 minutes to 1 hour before having breakfast. Your doctor will adjust your dosage based on how you respond and when you reach typical thyroid hormone levels.
It’s also recommended to take Synthroid oral tablet at least 4 hours before or after taking drugs or supplements that may lower its absorption. These include iron and calcium supplements and antacids. Synthroid may not work as well if taken with or near the time you take these and certain other medications.
Your doctor may advise that you take this medication around the same time each day. This helps keep a consistent amount of the drug in your body. And that can help the drug work more effectively.
Swallow the tablets whole. If a child can’t swallow Synthroid oral tablets, the tablets can be crushed and dissolved in 5–10 milliliters (mL) of water. This suspension should then immediately be given by a spoon or a dropper. The child should be sure to swallow the entire suspension.
If it’s hard for you to swallow tablets, view this article. It provides suggestions on how to swallow medications that come in pill form.
Also, be sure to talk with your doctor or pharmacist if you’re having difficulty taking your medication. They can offer recommendations about taking it.
Synthroid coupon
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Get free cardOverdose of Synthroid
It’s important that you do not take more Synthroid oral tablet than your doctor prescribes. Doing so can lead to harmful effects.
Symptoms of Synthroid overdose
Symptoms of an overdose can include:
- increased appetite or weight loss
- fever or excessive sweating
- nervousness, anxiety, or irritability
- insomnia (trouble sleeping)
- confusion
- tremors, muscle weakness, or muscle spasm
- palpitations
- increased heart rate and blood pressure
- dyspnea (trouble breathing)
- diarrhea or vomiting
- flushing or rash
- coma
What to do if you take too much Synthroid
If you think you’ve taken too much Synthroid, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have severe symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.
What to ask your doctor
This article describes the usual recommended dosages for Synthroid oral tablet. If your doctor prescribes this medication, they’ll determine the dosage that’s best for you.
Do not change your dosage of Synthroid oral tablet without your doctor’s recommendation. You should take Synthroid oral tablet exactly as your doctor prescribes it. Let your doctor know if you have concerns or questions about your treatment plan.
Here’s a list of some possible questions you may want to ask your doctor:
- How often will you need to change my dosage of Synthroid oral tablet?
- Will you change my dosage of Synthroid oral tablet if my current dosage isn’t working for my condition?
- How will I know when the dosage of Synthroid oral tablet is right for me?
- Do you need to change my dosage of Synthroid oral tablet if I’m taking other drugs with it?
- Would a different dosage of Synthroid oral tablet raise or lower my risk of side effects from the drug?
Boxed warning for Synthroid
Synthroid has a boxed warning about it not being used to treat obesity or as a weight loss aid. A boxed warning is the most serious warning from the FDA.
In people with typical thyroid function, usual dosages of Synthroid oral tablet aren’t effective for weight loss. And larger doses could lead to serious or life threatening toxicity, especially when used with certain weight loss drugs. This could lead to symptoms of an overdose, which may include palpitations, confusion, or coma.
For details, see the “Overdose of Synthroid” section above. You can also talk with your doctor to learn more.
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.