What Does a Hashimoto’s Attack Feel Like? Causes, Symptoms, and Treatments

One day, your Hashimoto’s symptoms feel manageable. The next, getting through your normal routine takes far more energy than it should. You may wake up exhausted despite sleeping all night, struggle to think clearly, feel unusually achy or weak, or notice several familiar symptoms getting worse at once.

People with Hashimoto’s often describe periods like these as an “attack” or flare-up. While a Hashimoto’s attack isn’t an official medical diagnosis, the sudden change in how you feel can be very real and difficult to ignore.

So, what does a Hashimoto’s attack feel like, what can trigger one, and how can you manage worsening symptoms? Below, we’ll look at the common signs of a Hashimoto’s flare-up, possible causes, and steps that may help you feel better.

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A Hashimoto’s attack is a term commonly used to describe a period when a person's Hashimoto’s symptoms suddenly become more intense or new symptoms appear. This is also called a Hashimoto’s flare-up. 

During these periods, symptoms like extreme tiredness, brain fog, muscle or joint pain, feeling cold, constipation, or mood changes can become more noticeable or difficult to handle.

The term “Hashimoto’s attack” is not an official medical term, and there is no specific test to confirm a flare-up. If your symptoms suddenly change or get much worse, your healthcare provider can help figure out if they are caused by Hashimoto’s, your thyroid hormone levels, your medication, or something else.

For many people, a Hashimoto’s attack or flare-up can feel like a sudden wave of exhaustion and physical discomfort that makes everyday activities much harder than usual. You may feel unusually weak or weighed down, have trouble concentrating, or notice that symptoms you normally manage well have suddenly become more intense.

Common symptoms during a flare-up include:

• Fatigue and body aches
• Brain fog or memory issues
• Muscle weakness or joint pain
• Constipation
• Depression or low mood
• Hair loss or dry skin
• Sensitivity to cold
• Sudden or unexplained weight gain

Some people may also experience temporary symptoms associated with an overactive thyroid, such as anxiety, a rapid heart rate, irritability, or difficulty sleeping. These symptoms can occur when inflammation affects the thyroid and causes thyroid hormones to be released into the bloodstream.

If you’re looking for extra help managing Hashimoto’s symptoms, a personalized nutrition plan can work alongside your current care. Dr. Donna Sergi at HealthierU offers nutrition guidance tailored to your needs and health goals, including natural treatment for Hashimoto's. Find out more about HealthierU’s support and book a consultation.

It can sometimes be difficult to tell whether your symptoms are part of your usual thyroid condition or a temporary flare-up. One of the clearest differences is a noticeable change from your baseline. Symptoms you normally experience may suddenly become more intense, or several symptoms may appear at the same time.

For instance, you might usually feel a bit tired, but then suddenly feel very worn out even if you have slept well. You could also notice more brain fog, aches in your muscles or joints, or feel colder than usual. Noticing these changes can help you spot patterns and talk about them with your healthcare provider.

In some cases, Hashimoto’s can briefly cause symptoms associated with an overactive thyroid due to the release of stored thyroid hormones into the bloodstream.

Hashimoto’s flare-ups can be triggered by a variety of factors that affect the immune system and thyroid function. While some triggers are outside your control, others are related to lifestyle, stress, illness, medication, or nutritional factors. Understanding these common causes can help you recognize patterns in your symptoms and take steps to manage them.

When you have an illness or infection, your body is under extra stress, which can make Hashimoto’s symptoms stand out. While you are sick, you might notice that fatigue, muscle aches, weakness, or brain fog feel stronger as your body heals.

Infections can sometimes affect the thyroid in ways that are not caused by a Hashimoto’s flare-up. For instance, subacute thyroiditis is a type of thyroid inflammation that can happen after a viral infection. This condition can cause thyroid pain and, for a short time, high levels of thyroid hormone in the blood, which is often followed by a period of low thyroid hormone levels.

If your thyroid symptoms get much worse during or after being sick, watch for any new or unusual signs. A fast heartbeat, unexplained weight loss, or pain or swelling in your neck could mean there is a change in your thyroid function or a different thyroid problem, not just a usual Hashimoto’s flare-up. Your healthcare provider can run thyroid tests and other checks to find out what is causing the change.

Hashimoto’s disease causes your body to attack the thyroid, which gradually causes damage that limits thyroid function (hypothyroidism). Normal functioning thyroids produce thyroid hormones called thyroxine (T4) and triiodothyronine (T3), which support metabolic needs and homeostasis. 

Without thyroid hormones, your body slows down the way it processes energy. The reduced energy production causes fatigue and other Hashimoto’s attack symptoms. To supplement the body’s inability to produce thyroid hormones, you may be prescribed a hormone supplement called levothyroxine. 

Hashimoto’s symptoms may become more noticeable when thyroid hormone levels are not adequately controlled. Medication-related factors can also affect thyroid hormone levels. For example, missing doses or taking levothyroxine inconsistently can make treatment less effective, while certain foods, supplements, and medications can interfere with how well the body absorbs it.

If your symptoms get worse or you still notice signs of hypothyroidism even though you are taking your medication as prescribed, contact your healthcare provider. They may suggest thyroid blood tests to check your hormone levels or see if your medication dose needs to be adjusted. Always talk to your provider before changing your dose or stopping your thyroid medication.

Physical and mental stress can make autoimmune disorders like Hashimoto’s disease worse. When you undergo a lot of stress, it can affect your immune system and hormone levels, which may make your symptoms feel more intense. 

Stress can affect several areas of your health, including:

• Worsening inflammation
• Changes in immune regulation
• Hormone imbalances
• Poor sleep and fatigue

These effects can make it harder to deal with symptoms like tiredness, brain fog, trouble sleeping, or muscle and joint pain. Stress can also affect your thyroid health in other ways, like when it disrupts your sleep, eating habits, exercise, or daily routines.

Stress is not always emotional. Physical stress from being sick, getting hurt, doing too much, or not sleeping enough can also affect how you feel. If you see that your symptoms get worse during stressful times, try to notice any patterns and find healthy ways to manage stress. This can help you take better care of your thyroid health.

Vitamin deficiencies have been linked to the triggering and exacerbation of Hashimoto’s disease. Nutritional deficiencies that may further affect thyroid function and contribute to worsening symptoms include:

• Vitamin D: Vitamin D deficiency has been correlated with higher concentrations of anti-thyroid antibodies and increased thyroid-stimulating hormone (TSH). When this vitamin deficiency is addressed, some studies have found reductions in thyroid antibodies and TSH, although research on vitamin D supplementation in Hashimoto’s is mixed. Foods that contain high amounts of vitamin D include: 
  
  
• Mushrooms
• Dairy products
• Eggs
• Liver
• Soy
• Oily fish
• Fortified foods
  
  
• Zinc: Zinc is vital for the synthesis of thyroid hormones. A zinc deficiency can result in decreased hormone production and a slowed metabolic rate. Foods that are high in zinc include:
  
  
• Seafood
• Red meat
• Cashews
• Chickpeas
• Oats
• Seeds
• Tofu
  
  
• Selenium: Selenium contributes to the antioxidant defense of the thyroid by helping the body manage oxidative stress associated with thyroid hormone production. Selenium is not produced by the body, so it must be obtained through food or supplements. Foods that contain selenium include: 
  
  
• Pork
• Beef
• Poultry
• Fish
• Nuts
• Beans

If you think a vitamin or nutritional deficiency might be causing your symptoms, ask your doctor about testing or dietary changes. A nutrition specialist can work with you to create a plan that supports your health and fits with your thyroid treatment.

Dr. Donna Sergi at HealthierU can help you create a nutrition plan tailored to your needs. To find out more about our nutritional support or to book a consultation, contact us today.

When Hashimoto’s symptoms suddenly get worse, the first step is figuring out what may be contributing to the change. Because Hashimoto’s symptoms can worsen for different reasons, consider factors like thyroid treatment, nutrition, sleep, stress, and overall health.

If your symptoms suddenly get worse, check that your thyroid treatment is still right for you. Take levothyroxine as your doctor prescribed and get your thyroid hormone levels checked regularly to see if your medication is working well. Always talk to your healthcare provider before changing your dose or stopping your medication.

Working on gut health, making changes to your diet, and lowering both physical and emotional stress are also common ways to support your health during a flare-up.

People with autoimmune conditions need to support their immune systems to help keep them healthy. The gut is important for immune function, and studies have found that people with Hashimoto’s thyroiditis have different gut bacteria compared to those without the condition.

Thyroid problems like Hashimoto’s disease are often linked to gut issues, including dysbiosis. Dysbiosis means the balance of microorganisms in the gut is disrupted, which can affect metabolism and the immune system.

The lining of your intestines works as a barrier, keeping the contents of your digestive tract separate from the rest of your body. Studies have found a link between autoimmune thyroid disease, changes in gut bacteria, and problems with this barrier. Still, more research is needed to know if these changes actually cause Hashimoto’s disease or its symptoms.

You can support your gut health by eating a balanced diet with plenty of nutrients, enough fiber, and a variety of minimally processed foods. Although probiotics and other ways to improve the microbiome are being researched, there is not enough strong evidence yet to recommend them for thyroid disease.

Stress and diet are said to be two of the biggest instigators of inflammation. Eating foods that are high in nutrients and steering clear of those that make your symptoms worse can help your health and thyroid function. However, there is no single diet proven to prevent or treat Hashimoto’s disease, and everyone’s needs are unique.



Foods that may support thyroid function and overall health include:

• Fish rich in Omega-3 fatty acids
• Nuts 
• Whole grains
• Berries
• Eggs
• Yogurt

Foods you may want to limit to help manage Hashimoto’s symptoms include:

• Fried foods
• Foods high in sugar
• Gluten
• Excessive alcohol
• Foods high in sodium

Some people also choose to avoid gluten, but a gluten-free diet is not recommended for everyone with Hashimoto’s disease. Recent research suggests there isn’t enough evidence to recommend a gluten-free diet for people with Hashimoto’s who do not have celiac disease.

Eating a balanced diet, staying active, and keeping up healthy habits can all help you feel your best. If you are thinking about making big changes to your diet, check with your healthcare provider or a nutrition expert to be sure you are still getting the nutrients you need.

Managing stress may help support thyroid health and well-being. However, the link between stress and Hashimoto’s disease is complicated, and more research is needed to understand how stress management affects the disease.

Stress reduction doesn’t have to be one big change. You can start slowly and implement practices like:

• Meditation
• Deep breathing
• Progressive muscle relations
• Yoga
• Light to moderate exercise

Finding stress-management strategies that fit into your daily routine may also help support better sleep, energy levels, and overall well-being. If you feel stress is significantly affecting your daily life or symptoms, consider discussing it with your healthcare provider.

Hashimoto’s flare-up symptoms can last for days or even weeks, especially if the cause is not addressed. During these periods, you may notice that fatigue, brain fog, muscle or joint pain, or sensitivity to cold feel more intense than usual.

If your symptoms last for several weeks, get worse, or do not get better with your usual treatment, contact your healthcare provider. Ongoing symptoms could mean your thyroid hormone levels or medication need to be checked, or that something else is affecting how you feel.

Sometimes, Hashimoto’s disease can briefly cause symptoms that look like an overactive thyroid. When thyroid cells are damaged, they can release stored thyroid hormone into the blood. This may lead to a fast heartbeat, anxiety, irritability, trouble sleeping, feeling too warm, or losing weight without explanation. Unlike Graves’ disease, where the thyroid keeps making too much hormone, this release is only temporary.

Let your healthcare provider know if you notice new symptoms or if your current symptoms worsen, especially if they last or make daily life harder. Testing TSH and T4 can show if your thyroid hormone levels are right and your treatment should be reviewed. If you have new symptoms like a very fast or irregular heartbeat, a swollen neck, or trouble swallowing, you should get checked by a doctor.

Yes, some people with Hashimoto’s disease still have symptoms like fatigue, brain fog, depression, feeling cold, constipation, or muscle and joint pain even when their thyroid tests are normal. These symptoms are not unique to Hashimoto’s and don’t always mean you are having a flare-up. If your symptoms continue but your thyroid tests are normal, your healthcare provider may look for other possible causes.

At HealthierU, we guide patients to better health and lasting wellness through nutrition and lifestyle advice. Dr. Donna Sergi brings decades of experience in holistic health and nutrition, and she is committed to providing each patient with personalized, natural care.

Dr. Sergi offers nutritional support tailored to each person’s needs and health goals. She considers how your diet and lifestyle may affect your well-being, and her care can work alongside the medical treatment you receive for Hashimoto’s disease.

If you’d like help managing Hashimoto’s symptoms and improving your overall health, book a consultation with HealthierU to begin your journey.