Does levothyroxine cause weight gain?

In this article:

• Levothyroxine weight gain
• Weight loss on levothyroxine
• Tips for weight management
• Alternatives

In this article

• Levothyroxine weight gain
• Weight loss on levothyroxine
• Tips for weight management
• Alternatives

It’s just a small gland in the front of your neck, but your thyroid plays a key role in a wide range of bodily processes. The thyroid hormones it produces affect your metabolism, breathing, growth, and mood. But, like all systems in your body, things can go haywire. Thyroid conditions occur when you have too much (hyperthyroidism) or too little thyroid hormone (hypothyroidism).

“Levothyroxine is a synthetic form of T4 (thyroxine), a thyroid hormone that is naturally produced by the thyroid gland,” explains endocrinologist Omayra Quijano-Vega, MD, a thyroid disease specialist with Paloma Health. “It is primarily used to treat hypothyroidism, a condition where the thyroid does not produce enough hormones.” Symptoms of hypothyroidism can include fatigue, weight gain, hair loss, and cold intolerance. By supplementing the missing hormone, levothyroxine helps restore normal thyroid levels and alleviate these symptoms.

Like any medication, there are some side effects of levothyroxine (also sold under the brand name Synthroid). It does not directly cause weight gain. Yet, you still might experience weight changes while taking this medication if your dose isn’t adequate to relieve your symptoms.

Can levothyroxine cause weight gain?

In short, no. “Levothyroxine itself is not directly associated with weight gain when properly dosed,” says Dr. Quijano-Vega. “Weight fluctuations on levothyroxine are typically due to under-treatment or over-treatment rather than the medication itself.” Indeed, it’s not the levothyroxine that can cause weight gain—it’s the condition for which people are taking it, which is hypothyroidism, or underactive thyroid.

“Hypothyroidism in general can cause decreased metabolism, which can cause weight gain,” says Romy Block, MD, an endocrinologist at Endeavor Health Medical Group in the greater Chicago area. According to the American Thyroid Association, this can lead to people with hypothyroidism burning fewer calories than usual, which can contribute to weight gain. Hypothyroidism can also cause salt and water retention, translating to an uptick on the scale. All told, a study in The Journal of Clinical Endocrinology & Metabolism found that 54% of hypothyroid patients reported weight gain as a symptom.

If you are experiencing changes in body weight on this prescription, it is likely that your dose of levothyroxine is not yet optimized to treat your hypothyroidism. “For example, if the dose is too low, unresolved symptoms of hypothyroidism such as weight gain may persist,” explains Dr. Quijano-Vega.

Does levothyroxine make it hard to lose weight?

If levothyroxine is doing its job to balance thyroid hormone levels, it should not hinder weight loss. In fact, it can make losing weight easier because weight gain is a symptom of hypothyroidism. However, if your dose is too low, it will be hard to lose weight because thyroid disorders affect your metabolic rate.

Tips for managing your weight on levothyroxine

If you are gaining weight or having trouble losing it while taking levothyroxine, the following expert-approved tips can help.

1. Ensure your dose is correct

Working with your healthcare provider to find the dose of levothyroxine that alleviates your symptoms is the most important step toward losing weight. “To prevent or counteract weight gain while on levothyroxine, ensure the dose is properly adjusted,” suggests Dr. Quijano-Vega. Your provider can run a panel of standard blood tests that check for normal thyroid function. Normal TSH values are between 0.5 and 5.0 mIU/L. When your results fall within the normal ranges, that means levothyroxine is doing its job and should not cause weight gain or hinder weight loss.

2. Favor protein and fiber

“Once thyroid levels are normalized, a holistic approach is recommended, including a balanced diet rich in lean proteins and fiber,” says Dr. Quijano-Vega. If your hypothyroidism is controlled with levothyroxine, you can make the same dietary changes as anyone else looking to lose weight—and upping your protein and fiber is a great place to start. Protein provides your muscles and cells with a sustainable energy source to keep your metabolism humming, while fiber promotes satiety to help manage appetite and cravings. At the same time, it’s smart to avoid foods that directly contribute to weight gain, such as sugary foods and processed foods.

RELATED: The best diet for weight loss

3. Prioritize sleep

Both Dr. Block and Dr. Quijano-Vega stress the importance of getting sufficient sleep for weight management, a recommendation that’s also supported by research. A study published in the journal Sleep found that people who are sleep-deprived consume more and unhealthier snacks between meals, which can contribute to weight gain, plus report higher levels of hunger. The result: People who sleep fewer than seven hours per night have significantly higher rates of obesity, according to separate research in Sleep.

Alternatives to levothyroxine

If you are diagnosed with hypothyroidism, levothyroxine is the first-line treatment. That said, it is not the best option for everyone—though this is typically for reasons that are not weight-related. “None of the thyroid medications cause weight gain if you are on the correct dose for your body,” says Dr. Block. Levothyroxine alternatives include:

Desiccated thyroid extract

Sold under the brand names Armour Thyroid and NP Thyroid, this is the most popular alternative to levothyroxine. This thyroid hormone replacement is made from the dried thyroid glands of pigs. Up to a quarter of hypothyroid patients in the U.S. prefer it to levothyroxine despite the fact that it is not technically an FDA-approved treatment—it was already widely used when the FDA began approving drugs in 1938, so it never had to go through the formal approval process.

A study published in the Journal of the Endocrine Society analyzed the experiences of 250 patients, half of whom took levothyroxine and half of whom switched to Armour Thyroid. They found that the top reasons for switching to Armour Thyroid were fatigue and an inability to lose weight, cited by 41% and 26% of patients, respectively. However, more than twice as many patients reported side effects on Armour Thyroid as those who were on levothyroxine.

Liothyronine

The other option is liothyronine (available as Cytomel), which is a synthetic version of triiodothyronine (T3), the active form of thyroid hormone. It is much more potent than levothyroxine and is absorbed much faster; therefore, closer monitoring by a thyroid specialist is required. It also has different potential side effects, one of which is weight loss, though others can be more serious, like chest pain and rapid or irregular heartbeat.

Be sure to seek medical advice from a healthcare professional to determine the best option for you.