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Can you gain weight if your thyroid medicine is too high?

It’s a common question for those with hypothyroidism who are taking thyroid hormone replacement medication like levothyroxine (Synthroid, Levoxyl, etc): Can your thyroid medication dosage be too high, causing unintended weight gain instead of helping with weight loss?

The quick answer is yes, it’s possible for your thyroid medication dosage to be too high and cause some weight gain instead of weight loss. However, it’s not extremely common. More often, being on too high of a thyroid medication dose can lead to symptoms like heart palpitations, tremors, trouble sleeping, diarrhea or rapid weight loss.

Still, let’s take a deeper look at the complex relationship between hypothyroidism, thyroid medication and weight changes.

How Hypothyroidism Causes Weight Gain

Hypothyroidism, or an underactive thyroid, happens when your thyroid gland does not make enough thyroid hormone. Thyroid hormone helps control many of the body’s functions, including regulating metabolism.

When your body’s metabolism slows down due to hypothyroidism, you burn fewer calories at rest. This can lead to weight gain if you continue to eat the same amount of calories per day.

Some of the main ways hypothyroidism contributes to weight gain include:

– Slowed metabolism. Your metabolism determines how many calories you burn just to sustain basic body functions. Thyroid hormone directly influences metabolism. Lower thyroid hormone levels slow your metabolism.

– Fatigue and less physical activity. Hypothyroidism can cause fatigue, low energy and exhaustion. This results in less physical activity and exercise, further reducing calorie expenditure.

– Fluid retention. Low thyroid hormone allows the body to retain more water, which adds to body weight on the scale.

– Loss of muscle mass. Hypothyroidism causes protein metabolism to become inefficient, leading to reduced muscle mass. Because muscle burns more calories than fat, this loss of lean muscle mass further slows metabolism.

How Thyroid Medication Helps With Weight Loss

The purpose of taking thyroid hormone replacement medication for hypothyroidism is to bring your thyroid hormone levels back up to normal. This relieves symptoms and reverses the metabolic changes that cause weight gain.

Here’s how getting your thyroid medication dosage properly adjusted can promote weight loss:

– Increases metabolism. Getting your thyroid hormone levels optimized normalizes your metabolism, allowing you to burn calories at a faster rate.

– Reduces fluid retention. At the right dosage, thyroid medication reduces excess fluid build up and swelling.

– Boosts energy. With hypothyroid fatigue and exhaustion relieved, you’ll naturally become more active and regain muscle mass.

– Normalizes appetite. Hypothyroidism can disrupt signals of satiety and fullness. Thyroid medication helps get appetite back to normal.

However, the benefits of thyroid medication on body weight rely on getting the dosage just right.

Can Thyroid Medication Dosage Be Too High?

Yes, it’s possible to end up on too high of a thyroid hormone replacement dosage.

With hypothyroidism, the goal of treatment is to normalize the thyroid stimulating hormone (TSH) level. TSH is released by the pituitary gland to signal to the thyroid to release more or less thyroid hormone as needed.

Doctors use the TSH level as an indicator of the body’s thyroid status and to guide appropriate thyroid medication dosing. The target TSH level for those treated for hypothyroidism is typically between 0.5 and 2.5 mIU/L.

If the TSH ends up below the expected reference range, such as less than 0.5 mIU/L, it usually indicates the thyroid medication dose is too high. This state is called subclinical hyperthyroidism or overmedication.

Being on too high of a thyroid hormone replacement dose overwhelms the body with more thyroid hormone than it needs. This can lead to symptoms opposite of hypothyroidism.

Signs Your Thyroid Medication Dose Is Too High

Here are the most common signs your thyroid medication dosage may be too high:

– TSH lower than 0.5 mIU/L
– Heart palpitations, rapid heart rate
– Hand tremors
– Trouble sleeping, restlessness
– Diarrhea or frequent bowel movements
– Unintended weight loss
– Muscle weakness
– Heat intolerance, increased sweating
– Anxiety or irritability

Symptoms are often more subtle in subclinical hyperthyroidism compared to overt or full hyperthyroidism. But over time, being on too high of a thyroid hormone dose can put strain on the cardiovascular system and bone health.

Let your doctor know if you experience any hyperthyroid-like symptoms on your current thyroid medication dosage. Your doctor can order labs to check your thyroid function, including TSH, and make any necessary thyroid medication adjustments.

Can Thyroid Medication That’s Too High Cause Weight Gain?

While unintended weight loss is more common, some research has found that excessive thyroid hormone replacement can also contribute to weight gain in certain situations.

A study in the journal Thyroid looked at weight changes in people with subclinical hyperthyroidism due to being on levothyroxine. It found:

– Patients with TSH under 0.1 mIU/L gained 3.7 lbs over 2 years
– Patients with TSH between 0.1 and 0.4 mIU/L gained 1.9 lbs over 2 years
– Patients with normal TSH lost 0.9 lbs over 2 years

Another study in the European Journal of Endocrinology found that nearly 50% of women who were overtreated for hypothyroidism experienced weight gain. Being on too high of a thyroid hormone dose was associated with more weight gain compared to those on an appropriate dose.

Researchers theorize that the following aspects of subclinical hyperthyroidism could promote weight gain in some people:

– Increased appetite and hunger
– Fluid retention
– Loss of bone mass
– Cellular changes in metabolism
– Triglyceride and cholesterol changes

However, more research is still needed to clarify the mechanisms. Weight gain due to overtreatment does not happen to everyone with a TSH under 0.5 mIU/L. But it remains a possibility if thyroid medication dose is not properly optimized.

Tips to Help Avoid Weight Gain on Thyroid Medication

To help prevent inadvertent weight gain related to your hypothyroidism treatment, here are some tips:

– Get TSH tested regularly. This helps detect if your dose needs adjusting before major symptoms occur. Tell your doctor if you have any hyperthyroid symptoms.

– Take your thyroid medication correctly. Be consistent, take your thyroid medication on an empty stomach, and avoid interactions with supplements and medications.

– Monitor your weight. Track your weight loss progress. Unexpected weight gain could signify your dosage needs tweaking.

– Eat a healthy diet. Focus on whole, unprocessed foods balanced in carbs, protein and fat. Limit added sugars and refined grains.

– Stay active. Get regular exercise tailored to your fitness level. Strength training helps build metabolism-boosting muscle.

– Prioritize sleep. Aim for 7-9 hours per night. Poor sleep disrupts metabolism-regulating hormones.

– Manage stress. High stress drives up cortisol, which can promote fat storage. Make time for stress-reducing activities.

– Check for other issues. Rule out health conditions like insulin resistance that could affect weight independently from thyroid status.

With an appropriate thyroid hormone replacement dosage tailored to your body’s needs, you should be able to gradually lose excess weight gained from hypothyroidism.

The Bottom Line

While not extremely common, it is possible for your thyroid medication dosage to end up too high and actually cause some weight gain instead of continued weight loss.

This occurs if your thyroid hormone levels are not properly optimized and your TSH ends up lower than the target range. Being on too much thyroid medication can overwhelm your body and lead to mild hyperthyroid symptoms.

Research shows that a thyroid-suppressing TSH under 0.5 mIU/L may promote subtle fluid retention and metabolic changes that contribute to weight gain in some people.

To prevent this, work with your doctor to find your optimal thyroid medication dosage based on your TSH and symptom response. Monitor your weight and let your doctor know if you experience any hyperthyroid-like reactions.

With proper thyroid treatment, you can get your metabolism and weight loss efforts back on track. But medication dosage adjustments take time and patience. Stick with your treatment plan and have your thyroid levels rechecked as needed until your body regains ideal balance.