Understanding Thyroid Medication And Weight Loss

Hypothyroidism can leave you feeling tired, cold, and experiencing muscle and joint pain, but the most commonly discussed symptom is weight gain. For those with this hormone disorder, losing weight and keeping it off can be a real challenge. Hypothyroidism can be controlled with thyroid medication, so many people naturally think that taking that medication will help them to shed pounds.

There are many myths and assumptions around the impact of thyroid medication on weight loss. It’s important to be realistic about exactly what thyroid medication can and can’t do for your weight. 

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How does thyroid medication affect your weight?

Hypothyroidism is a hormone-related condition where your thyroid glands don’t create enough of the thyroid hormone. Similar effects are also seen in cancer patients who have their thyroid glands surgically removed. The thyroid hormone plays an important role in controlling your metabolism and body temperature. Because of this, if you produce enough o the thyroid hormone, you may experience common symptoms, such as:

  • Sensitivity to cold 

  • Fatigue 

  • Constipation 

  • Muscle and joint soreness and/or stiffness

  • Dry skin 

  • Weight gain¹

A lack of or low levels of the thyroid hormone often slows down your metabolism, making it harder for your body to burn energy and keep off weight.

Losing weight when you have hypothyroidism isn’t as simple as just taking thyroid medication. While weight gain is a common symptom reported in patients with hypothyroidism, thyroid disorder is not necessarily the sole reason for this weight gain.

There are many reasons why someone might gain weight. Overeating or menopause, for example, could be contributing factors. Because of the variability behind why weight gain occurs, taking thyroid hormone medication is unlikely to be a cure-all for weight gain by itself.

How long after starting thyroid medication will I lose weight?

When you start taking thyroid medication like levothyroxine, don’t expect instant weight loss. The first barrier is getting the right dose of thyroid medication. Once you have reached your ideal dose, you may notice some weight loss after around three to six months of continuous use.

It’s important to keep in mind that weight loss isn’t a universal side effect of thyroid medication. For example, a 2014 study found that only 52% of patients with diagnosed hypothyroidism lost weight after taking thyroid medication. For patients who did lose weight, they lost on average 3.8 to 4.4 lbs after five months of treatment.²

Losing excess water weight is also a common reason why patients notice a difference in their weight after taking thyroid medication, rather than fat loss. One study found that after a year of treatment with thyroid medication, patients’ experienced a significant reduction in their body weight. However, this weight loss did not affect the amount of fat or bone mass each patient had, leading researchers to conclude that the weight loss was likely due to the excretion of excess water that can build up as a result of hypothyroidism.³

Can levothyroxine be used as a weight-loss tool?

Thyroid medication has garnered a reputation as a weight-loss tool due to its potential to help patients with thyroid issues lose weight. Because of this, certain thyroid medications like levothyroxine can be seen purely as a weight-loss tool.

The reason why thyroid medication would be prescribed exclusively for weight loss is due to its ability to increase metabolism and help individuals to burn more energy.

However, it’s important to note that taking thyroid medication for weight loss alone can be incredibly risky for your health, and it may not even be effective for weight loss.

Thyroid medication is specifically formulated to treat thyroid disorders. Taking thyroid hormones when you don’t have hypothyroidism can result in symptoms similar to hyperthyroidism, which is a condition where your thyroid produces too much of the thyroid hormone.

Symptoms of hyperthyroidism include:

  • Increased heart rate, palpitations, and dangerously irregular heart rhythms

  • Loss of bone density

  • Sensitivity to heat

  • Anxiety

  • Insomnia

  • Diarrhea

  • Shakiness/nervousness⁴

Mildly elevated thyroid levels or mild hyperthyroidism can result in increased appetite and may therefore even cause weight gain. Not only could taking thyroid medication when you don’t have hypothyroidism leave you with a range of negative side effects, but it also might have the opposite effect of the weight loss you were hoping for. 

Other ways to lose weight when you have thyroid issues

Taking thyroid medication does not guarantee weight loss. If you have hypothyroidism and are struggling to keep your weight down even with the help of medication, there are a range of other strategies that may assist with weight loss.


When your metabolism slows down, as it does with hypothyroidism, you can’t burn calories at the rate you would if your thyroid was functioning normally. Whether you're resting or exercising, you will burn fewer calories than someone with a faster metabolism doing the same activity. Implementing simple tips for a healthier diet and reviewing your total caloric intake can help.

Since you burn fewer calories when you have hypothyroidism, you may want to track and slightly reduce your calories in order to lose weight. You might be surprised by the caloric load of certain food and drink. Reducing, replacing, or removing these from your diet could make a big difference to your weight over time.

High-calorie food to watch for include:

  • Soda – A 12 oz regular Coca-Cola contains 140 calories, while Diet Coca-Cola contains zero calories. However, as Diet Coca-Cola contains artificial sweeteners, you may also want to avoid it if you are aiming to make your diet healthier.

  • Condiments – Dressings like ranch can be deceptively high in calories and offer limited nutritional benefits. One serving of ranch dressing contains around 145 calories. 

  • Candy – Just four pieces of Twizzlers contain 133 calories. Treating candy as a sometimes food and not part of your everyday routine can make a big difference to your calorie intake and help you lose weight.

You could also see a dietitian for guidance on nutrition and the types of diets that are right for you and your goals. 


Cardiovascular exercise is a great way to burn calories and help keep off the extra weight that can build up thanks to a slow metabolism when you have hypothyroidism. Just an hour a day of physical activity not only helps you to lose weight, but also improves your overall health, energy levels, and mental state.

Examples of cardio exercise include:

The lowdown

When you have hypothyroidism, weight gain can be a difficult symptom to deal with. While taking thyroid medication can help you to lose weight, it is not a cure-all, and it doesn’t work for everyone.

Even if thyroid medication is effective for you, your doctor will likely recommend that you support your weight loss efforts with additional strategies like diet and exercise.

It is especially important to avoid taking thyroid medication for weight loss alone when you don’t have hypothyroidism, as this can lead to serious side effects such as hyperthyroidism, which will also require treatment.

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