Thyroid medication and weight loss: How long until I lose weight?

One of the big questions that many people have after starting hypothyroid medication is ‘How long after starting the thyroid medication will I lose weight?’. Since one of the most common symptoms of hypothyroidism is weight gain, it’s easy to see why many people want to know how quickly they will lose weight once they’ve started treatment. Unfortunately, the answer is often not as straightforward as many people hope. The link between your weight and thyroid is complex and involves several factors. This article will help you to understand what weight loss you can expect after starting thyroid medication, and how you can support it.

Understanding thyroid disease 

Your thyroid is a small gland that sits under the skin at the front of your neck. It’s part of your endocrine system and is responsible for producing the hormones thyroxine (T—4) and triiodothyronine (T—3). These hormones play a role in every cell of your body by supporting your body's metabolism and helping with your body’s temperature control. Your metabolism is your body’s ability to turn the food you consume into energy.

There are two different types of thyroid disease:

• Hypothyroidism: Also called ‘underactive thyroid’, it happens when the thyroid gland doesn’t produce enough of the thyroid hormones.
• Hyperthyroidism: Also called an ‘overactive thyroid’ this is when the thyroid gland produces too much of the thyroid hormones.

In this article we’re discussing hypothyroidism and the medications used to treat it.

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Hypothyroidism

Underactive thyroid, the most common thyroid disease, can result from various causes including autoimmune conditions, neck surgery, or certain medications.

Symptoms of hypothyroidism often start gradually, but over time you might notice:

• Tiredness
• Sensitivity to the cold
• Constipation
• Dry skin
• Weight gain
• Puffy face
• Coarse hair and skin
• Joint pain and muscle aches
• Depression
• Memory problems

Hypothyroidism is treated by taking a synthetic form of the hormone thyroxine called levothyroxine (synthroid, Levo—T). This brings your thyroid hormone levels back to normal.

Hypothyroid medication and weight loss

One of the most common symptoms of hypothyroidism is weight gain. According to the American Thyroid Association (ATA), hypothyroidism leads to a modest weight gain, due to the combination of having a slower metabolism and increased water retention. The ATA states that most people gain about 5–10 pounds due to hypothyroidism, although it can depend on the severity of hypothyroidism.

How long after starting thyroid medication will I lose weight?

Because weight gain is a common symptom of hypothyroidism, it’s understandable that you might expect to lose weight once your thyroid hormones are back in balance. However, this isn’t the case for everyone, research from the Boston University Medical Center found that only 52% of patients lost weight in the first 2 years after starting hypothyroid medication, and this weight loss was modest with the mean amount of weight lost being around 8 pounds. 

However the ATA also notes that treating hypothyroidism will return your body weight to what it was before the hypothyroidism started, so if your hypothyroidism caused you to gain weight, then once you have started thyroid medication you may see some weight loss. However, there are many different causes for weight gain so it’s possible that your weight gain is due to a combination of factors, in which case thyroid medication alone won’t reverse it.

Here’s a general timeline on how weight loss after starting thyroid medication might look: 

• First few weeks: Once you begin treatment you will notice a gradual reduction in the symptoms of your hypothyroidism including a reduction in water retention, this could lead to the loss of a few pounds, remember though it’s likely the weight loss is due to water loss not fat loss.
• 1–3 months: As your metabolism improves, your ability to lose weight will return to your pre—hypothyroidism level. In combination with a healthy lifestyle you may start to see a subtle change in your weight.
• Beyond 3 months: If you’re on the right dose, your thyroid hormones will be back in the normal range and you should see a significant improvement in your hypothyroidism symptoms.   

Factors that influence weight loss 

How much, and how quickly, you could lose weight after starting hypothyroidism medication will depend on several factors:

1. Medication adherence and dosage. Taking your medication consistently and being on the optimal dose will ensure that your hormone levels return to normal quickly. If your dose is too low, or you don’t take your medication regularly, then your metabolism may remain sluggish and inhibit any weight loss.
2. Baseline health. According to the ATA, only about 5–10 pounds of weight gain is usually related to the thyroid, although this depends on the severity of hypothyroidism. Once your thyroid hormones are back to normal then you should expect to lose the weight you gained from hypothyroidism. However, most of this weight is due to water retention, and it’s ‘water weight’ that you will lose, not fat. Taking thyroid medication will not lead to you losing weight that is due to other health conditions like obesity or insulin resistance disorders. 
3. Diet and exercise. Lifestyle choices like your diet and exercise levels will play a massive role in how much weight you lose. While your metabolism will return to its pre—hypothyroid levels, if you’re not making healthy lifestyle choices then you’re unlikely to see significant changes in your weight. 
4. Other factors. Once the symptoms of your hypothyroidism have resolved, you might find that you have more energy and other symptoms like muscle or joint pain and weakness have eased. This can make it easier to exercise and make healthy lifestyle choices, which in turn can help you to lose weight in a sustainable fashion. 

Setting realistic expectations

Taking thyroid medication when you have hypothyroidism can help you feel better and improve your overall health. However, it's not a magic solution for weight loss. The primary goal of treatment is to restore your body’s normal function, which for some people will result in modest weight changes. Many people feel better in terms of energy and mood long before they notice significant changes on the scale. 

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Important to know: You should never take thyroid medication to help you lose weight if you don’t have a thyroid disorder as it can lead to dangerously high levels of thyroid hormones and put you at risk of serious side effects such as heart palpitations, heart rhythm problems, and loss of bone and muscle mass.

When to consult your doctor

If you’re not seeing an improvement in your hypothyroid symptoms, or your weight gain persists after a few months of treatment then reach out to your healthcare provider. They may need to:

• Check your hormone levels and adjust your medication dose as required.
• Test for other conditions that might be causing your symptoms.
• Give you personalized guidance on how to best manage your weight.

Tips for supporting weight loss with hypothyroidism

While starting thyroid medication will help your metabolism to return to its normal rate, and can lead to a moderate loss of weight, there are additional steps you can take to support healthy and sustainable weight loss that will help you achieve long—term changes.

• Eating a balanced diet. Focus on nutrient dense food like lean proteins, whole grains, vegetables, fruits, and healthy fats. Limit processed foods or those with refined sugar. It can be very difficult to overhaul your diet so start by making one sustainable change at a time. For example start by switching out refined grains for whole grain e.g switch white bread/pasta/rice for the whole grain variety.
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• Regular moderate exercise. The CDC recommends that adults get at least 150 minutes (2.5 hours) of moderate—intensity physical activity a week. They should also aim to do two muscle—strengthening activities a week like weight training. Depending on your current fitness levels, moderate—intensity activity is anything that raises your heart rate, breathing rate and causes you to break a sweat. You should be able to talk, but not sing a song while doing it. This could include anything from a brisk walk to playing tennis, whatever your preference. 
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• ‍Manage stress. Practicing stress-reduction techniques like meditation, yoga, deep breathing or mindfulness can help to lower your cortisol levels and support your overall health.
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• ‍‍‍Prioritize sleep. We know it can be difficult, but getting 7–9 hours of good quality sleep a night can help your physical, mental and emotional health. A 2022 narrative review published in the journal ‘Nutrients’, found that poor sleep can alter your metabolism and increase your craving for foods rich in fat and carbohydrates. Together this can have a negative impact on weight loss.

The final word

Taking thyroid medication for hypothyroidism helps restore your thyroid hormone levels to normal. This will regulate your metabolism and enhance your overall well-being. Thyroid medication itself can result in a moderate amount of weight loss for some people, however, it’s mostly due to a loss of water rather than fat loss. 

Many people find that once their thyroid hormone levels are back to normal, they have more energy and generally feel better. This improved overall well-being can help you to make healthy lifestyle choices which can lead to long—term and sustainable weight loss.

If you’re struggling to lose weight, or your other hypothyroid symptoms have not resolved, then reach out to your healthcare provider. They will be able to offer personalized guidance to help you reach your goals and may suggest any further tests or treatments you may need.