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9 Synthroid Side Effects That Might Mean Your Dosage Is Way Off

Synthroid Side Effects

Ever thought about your thyroid? Try this quick check: place your hand on your throat and swallow. Notice the bump that moves? That’s your Adam’s apple, and just beneath it sits your thyroid. This small gland may be easy to overlook, but it’s crucial—it functions like your body’s main control center. The hormones it produces influence nearly every system in your body, and you usually don’t notice it’s there—until something goes off balance. If your thyroid isn’t working as it should, it could be a sign that the dosages of your Synthroid tablets need adjusting. We’ll discuss the 9 side effects of Synthroid further in this blog, which might indicate that your dosage isn’t quite right. Let’s start!

How Synthroid Works to Treat Hypothyroidism?

Hypothyroidism occurs when your thyroid gland doesn’t produce enough hormones, leading to symptoms like weight gain, fatigue, and a slower heartbeat. While that covers hypothyroidism, there’s also hyperthyroidism, which involves the thyroid producing too much hormone—but that’s a different story. 

Synthroid, or levothyroxine sodium, is a synthetic version of thyroid hormone. Despite being lab-made, it’s identical to the hormone naturally produced by your body. Dr. Melanie Goldfarb, an endocrinologist and thyroid expert at Providence Saint John’s Health Center in Santa Monica, California, explains, “Synthroid effectively replaces the hormones your thyroid isn’t producing enough of.”

While Synthroid is generally well-received and makes most people feel much better, it’s not without potential side effects. However, Dr. Goldfarb notes, “These side effects are usually more about finding the right dosage than issues with the medication itself.”

It’s worth noting that about 1% of patients may not respond to Synthroid and could require alternative treatments. Yet, the majority of those who start Synthroid often report feeling significantly better within six weeks. To ensure your treatment is on point and you’re not in the small group who might not benefit from Synthroid, let’s explore some signs to watch for that might suggest your dosage needs adjustment:

Your Heart Is Pounding Too Much

When your heart is fluttering—and it’s not from celebrity sightings. When it comes to dosing Synthroid, it’s primarily based on your weight. This approach generally works well, but occasionally, it might lead your thyroid to become a bit too enthusiastic, tipping you into hyperthyroidism. A telltale sign of this? Your heart might start to race or beat irregularly, explains Dr. Goldfarb. If you notice your heart behaving unusually, it’s crucial to contact your doctor promptly. Whether or not it’s related to your medication, it’s essential to rule out any other potential issues. 

Fluctuations in Your Weight

Your thyroid plays a significant role in regulating your weight and appetite, which means any imbalance can lead to sudden weight changes. Dr. Goldfarb points out that if you find yourself outgrowing your clothes unexpectedly, it might be a sign that your Synthroid dosage is too low. On the flip side, if you’re suddenly dropping pounds without trying, your dosage might be on the higher side.

Excessive Sweating

It’s normal to break a sweat during a tough workout, but finding yourself soaked in sweat outside of the gym? That’s less ideal. While some of us naturally tend to sweat more than others, a sudden increase in sweating—including night sweats—could be linked to your Synthroid medication. Dr. Goldfarb assures that while it’s not something to panic over, it’s definitely worth mentioning to your doctor during your next visit.

Early or Irregular Menstruation

Your thyroid gland plays a key role in regulating your menstrual cycle. In fact, one of the common signs of hypothyroidism in women is having irregular periods. Starting on Synthroid is generally expected to stabilize your cycle, which is great, but it might catch you off guard if you’ve grown accustomed to less predictable periods.

Digestive Disruptions

It’s not the most pleasant topic, but it’s important to discuss: stomach upsets and diarrhea are somewhat common when adjusting to Synthroid. Your hormones influence every part of your body, including your digestive system. These symptoms typically settle down as your thyroid hormone levels become more balanced. 

Headaches That Stick Around

Just as PMS often sends us reaching for chocolate, hormonal changes can bring on headaches. Adjusting your hormone levels with Synthroid might initially lead to some serious headaches. Interestingly, many women report that their chronic headaches actually improve once their body adjusts to the medication. 

Getting Too Much Anxious

Anxiety is a common part of life for many, but if you’re feeling excessively worried or on edge more than usual, it might be a clue that your thyroid is overactive. This could suggest that your Synthroid dosage is too high, explains Dr. Goldfarb. You don’t have to endure this alone; if you’re experiencing unusual anxiety, feelings of mania, or depression after starting your medication, discuss these changes with your doctor. 

Losing More Hair Than Usual

If you’re finding clumps of hair in the shower or noticing thinner eyebrows, it could be a sign of low thyroid function. These symptoms can also occur if your Synthroid dosage is too low. While many women see an improvement in these symptoms as their medication begins to work, ongoing hair loss isn’t something to ignore. If you’re still experiencing these issues, talk to your doctor. 

Rashes and Reactions

Did you know not all generic forms of Synthroid are exactly the same? According to Dr. Goldfarb, this can sometimes lead to unexpected side effects. While most women adjust well to the various generics, a few might react to the additional ingredients in these pills. If you’re experiencing a rash, fever, exhaustion, or hives, it’s important to consult with your doctor right away. They might recommend switching to a different generic or possibly prescribing the brand-name medication to see if that alleviates the problem. 

While it’s important to know and take your doses correctly, it’s also important to buy them from a safe place, such as the best Canadian online pharmacy, to ensure the medication’s safety and efficacy.


Synthroid is a widely used medication for treating hypothyroidism, and for most individuals, it brings about a significant improvement in symptoms. However, like any medication, it can have side effects, particularly if the dosage is not correctly adjusted to your body’s needs. It’s essential to monitor your body’s response to Synthroid and report any unusual symptoms to your healthcare provider. Adjustments to your dosage can often alleviate these side effects, ensuring that the medication effectively manages your thyroid levels without compromising your overall well-being. Remember, effective communication with your healthcare provider is key to finding the right balance and ensuring that Synthroid works optimally for you.

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