Table of ContentsView AllTable of ContentsThyroid MedicationsSigns and SymptomsCauses and Risk FactorsTests and MonitoringWhen to See a Healthcare ProviderFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Thyroid Medications
Signs and Symptoms
Causes and Risk Factors
Tests and Monitoring
When to See a Healthcare Provider
Frequently Asked Questions
A fast heart rate andfatigueare just two of the signs your thyroid medication dose is too high.This can happen when thyroid hormone replacement drugs likelevothyroxineare used to treathypothyroidism(when a thyroid gland does not produce enough thyroid hormones).
Other symptoms of taking too much thyroid medication can include anxiety, diarrhea, weight loss, and trouble sleeping. It’s important to identify these side effects and tell your healthcare provider, so they can help you find the dose of levothyroxine that’s safe and effective.
This article will go over why you might be taking too much levothyroxine, the side effects of levothyroxine overmedication, and when to see a healthcare provider.
Thyroid Hormone Replacement Drugs
Levothyroxine is a type of thyroid hormone replacement drug that is often used to treat hypothyroidism.Brand namesfor levothyroxine include Synthroid, Levoxyl, and Tirosint.
Natural desiccated thyroid (NDT) is also used to treat hypothyroidism. For some people, NDTs work better than levothyroxine. Many people prefer NDTs because they are considered more natural. Brand names of NDTs includeArmourand Nature-Throid.
How Is Hypothyroidism Treated?
1:41Click Play to Learn More About the Dangers of Too Much Thyroid Medication
1:41
Click Play to Learn More About the Dangers of Too Much Thyroid Medication
Symptoms of Too Much Thyroid Medication
The signs and symptoms of thyroid hormone overmedication can vary but may include:
In some cases, the symptoms and side effects of taking too much levothyroxine are similar to those of hypothyroidism. For example, you may feel more exhausted than usual, achy (as if you have the flu), or jittery and anxious. You may also gain weight.
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How Levothyroxine Overmedication Happens
There are a number of ways you can end up taking too much levothyroxine. Sometimes, it takes trial and error to get your dosage just right. Prescribing mistakes can happen as well.
Dosage or Drug Quality Issues
If you are taking generic levothyroxine, you may receive a batch of medication that is more potent or less potent than your previous refill. Even a slight change of potency from one refill to the next can lead to over or undermedication and symptoms of hyperthyroidism or hypothyroidism.
Switching formulations of levothyroxine—for example, from tablet to gel caps or liquid—can also cause overmedication because your body absorbs some formulations of levothyroxine better than others.
For example, Tirosint liquid gel caps and Tirosint-SOL liquid levothyroxine are absorbed better than levothyroxine in tablet form. You might be prescribed gel caps or liquid levothyroxine if you are allergic to dyes or fillers, but making the switch could result in overmedication.
This is why close monitoring is important. Your thyroid stimulating hormone (TSH) level should be checked every six to eight weeks after beginning thyroid hormone replacement until the correct level is achieved.It also should be checked after changing the brand, formulation, or dose of your medication.
Diet Changes
Sometimes, you end up getting too much levothyroxine because of factors that are not directly related to the medication.
For example, changing your diet can affect how well your body absorbs thyroid hormone medication.
One situation where this could occur would be if you cut back on your fiber intake.When you make this change, you might start to absorb higher levels of thyroid medication.
How and When to Take Thyroid Hormone Replacements
Supplements and Medications
Taking certain supplements can add to the effects of your thyroid replacement medication and lead to you taking too much levothyroxine.
Pay close attention to supplements featuring the terms “thyroid support,” “energy support,” “thyroid glandulars,” “adrenal glandulars,” and “bovine glandulars.” Some of these supplements contain thyroid hormones from animals.
Supplements that containiodine, such as bladderwrack (Fucus vesiculosus), kelp,bugleweed, Irish moss, or seaweed can also cause problems. Too much iodine, in particular, can overstimulate your thyroid and trigger hyperthyroidism.
Drugs that contain estrogens, such as hormone replacement medications and oral contraceptive pills, can also interfere with thyroid hormone requirements.When you stop taking them, your body might need more or less thyroid medication than when you were taking them.
Hashimoto’s Disease
Medical conditions can also lead you to have too much levothyroxine in your body. WithHashimoto’s disease, your thyroid hormone levels can fluctuate rapidly.Hashitoxicosisoccurs when your thyroid is over-functioning and producing more thyroid hormone.
Taking your thyroid hormone replacement medication when your thyroid is in hashitoxicosis can temporarily cause symptoms of hyperthyroidism.
Pregnancy
You might have too much levothyroxine in your body if you’ve recently been pregnant. During pregnancy, your need for thyroid hormone increases. You may need to be prescribed a higher dose of medication than you usually take during this time.
However, your need for thyroid hormone decreases once you give birth. The dose of thyroid hormone replacement that you were taking during pregnancy could be too high for the postpartum period and could lead to overmedication.
Monitoring for Thyroid Overmedication
To avoid overmedication with levothyroxine, your healthcare provider will use your thyroid blood test results to see if you are getting too much. In some cases, having a TSH level that is lower than normal (or atriiodothyronine(T3) orthyroxine(T4) level that is higher than normal) can be a sign of overmedication.
A Word From Verywell
—DANIELLE WEISS, MD, MEDICAL EXPERT BOARD
Contact your healthcare provider if you’re experiencing symptoms of too much levothyroxine. They can do tests to check your thyroid levels and figure out if you’re being overmedicated.
If your provider determines that you are taking too much levothyroxine, they will reassess your treatment plan. They might advise you to change your diet if it’s contributing to thyroid overmedication. Your provider might also change your medication or adjust your dose.
What Do Your Thyroid Blood Test Results Mean?
Summary
There are a few reasons you could end up taking too much levothyroxine. For example, you may become overmedicated with the dosage or type of thyroid hormone replacement therapy you are taking. Certain health conditions and lifestyle changes can also make an overdose of levothyroxine more likely to happen.
The symptoms of too much thyroid medication can mimic hyperthyroidism or hypothyroidism, so it’s important to have your TSH, T4, and/or T3 levels checked regularly and any time your medication changes.
Being overmedicated with thyroid hormone replacement drugs typically is uncomfortable but rarely dangerous. Your healthcare provider can help you to change thyroid-boosting supplements and/or cut back on your medication dosage in order to avoid taking too much levothyroxine.
Frequently Asked QuestionsSide effects of levothyroxine can include hair loss, headache, diarrhea, fever, weight gain or loss, vomiting, joint pain, heat sensitivity, appetite changes, menstrual cycle changes, and leg cramps.Serious side effects that could warrant visiting a provider include wheezing, shortness of breath, hives, rash, and swelling of the hands, feet, ankles, or lower legs.There is no single recommended dosage for levothyroxine because each person’s body works differently.In many cases, people who start receiving treatment for hypothyroidism will be given a lower dose of medication to avoid the risk of overmedicating. Over time, their dose will likely need to be adjusted to meet their individual needs.There are many risks of taking too much levothyroxine. The signs and symptoms of thyroid overmedication include anxiety, diarrhea, depression, elevated heartbeat, elevated blood pressure, fatigue, irritability, difficulty concentrating, difficulty sleeping, being overheated, and unprompted or unintentional weight loss.
Side effects of levothyroxine can include hair loss, headache, diarrhea, fever, weight gain or loss, vomiting, joint pain, heat sensitivity, appetite changes, menstrual cycle changes, and leg cramps.Serious side effects that could warrant visiting a provider include wheezing, shortness of breath, hives, rash, and swelling of the hands, feet, ankles, or lower legs.
Side effects of levothyroxine can include hair loss, headache, diarrhea, fever, weight gain or loss, vomiting, joint pain, heat sensitivity, appetite changes, menstrual cycle changes, and leg cramps.
Serious side effects that could warrant visiting a provider include wheezing, shortness of breath, hives, rash, and swelling of the hands, feet, ankles, or lower legs.
There is no single recommended dosage for levothyroxine because each person’s body works differently.In many cases, people who start receiving treatment for hypothyroidism will be given a lower dose of medication to avoid the risk of overmedicating. Over time, their dose will likely need to be adjusted to meet their individual needs.
There is no single recommended dosage for levothyroxine because each person’s body works differently.
In many cases, people who start receiving treatment for hypothyroidism will be given a lower dose of medication to avoid the risk of overmedicating. Over time, their dose will likely need to be adjusted to meet their individual needs.
There are many risks of taking too much levothyroxine. The signs and symptoms of thyroid overmedication include anxiety, diarrhea, depression, elevated heartbeat, elevated blood pressure, fatigue, irritability, difficulty concentrating, difficulty sleeping, being overheated, and unprompted or unintentional weight loss.
14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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