If you’ve been diagnosed with Hashimoto’s thyroiditis, you may be wondering how to know if you are experiencing a flare-up and what to do next. This article shares 12 symptoms of a Hashimoto’s flare-up.

an image highlighting the thyroid in the human body.

What is Hashimoto’s Disease

Hashimoto’s disease (also known as Hashimoto’s thyroiditis) is an autoimmune disease. It causes your immune system to mistakenly attack your thyroid gland. 

Your thyroid gland is located at the front of your neck and produces hormones called triiodothyronine (T3) and thyroxine (T4). These hormones regulate the metabolism, influencing how quickly your body burns energy.

When the immune system attacks the thyroid gland, the production of these thyroid hormones can begin to fall. This can lead to a variety of health problems. 

Around 2% of the American population is affected by Hashimoto’s disease, with this autoimmune disorder more common in women than men in the United States. 

Many people diagnosed with Hashimoto’s disease later go on to develop hypothyroidism (an underactive thyroid). This is a relatively common condition, affecting around 5% of Americans. 

Overview of the Symptoms of Hashimoto’s Disease

The thyroid hormones are associated with all sorts of processes in the body.

In addition to your metabolism, thyroid hormones help to regulate things like your menstrual cycle, your body temperature, your energy levels, and even the growth of your hair and nails.

So when the level of thyroid hormones in your body is compromised, quite a wide range of symptoms can result. These symptoms vary from person to person and can develop slowly. They might also be quite vague and non-specific, meaning that they may initially be mistaken for other conditions.

Once Hashimoto’s disease has been diagnosed, it can usually be treated with a thyroid replacement hormone so that your hormonal balance is restored. As a result, your symptoms should improve or even disappear.

But sometimes, they can flare up again, usually because stress or a certain medication is affecting your thyroid function, or because something is preventing you from absorbing your medication properly.

When symptoms “flare up”, they usually come back quite abruptly and can feel much more intense. It’s important to recognize them when they happen and discuss them with your healthcare provider so that you can work on ways to bring your condition back under control.

a woman having her thyroid examined.

Symptoms of a Hashimoto’s Flare-Up

Here’s a look at the symptoms you might experience during a flare-up of Hashimoto’s disease, including:

  • Fatigue
  • Weight gain
  • Dry skin
  • Cold intolerance
  • Hair loss
  • Constipation
  • Depression
  • Memory problems
  • Muscle weakness
  • Irregular periods
  • Hoarseness
  • Neck swelling

1. Fatigue 

Fatigue is one of the main symptoms of Hashimoto’s – and also one of the most debilitating. 

Unlike the typical tiredness that you might experience after a restless night, fatigue associated with a Hashimoto’s flare-up is so extreme that it can affect your day-to-day activities. 

In part, it is caused by your lower hormone levels slowing down your metabolism. But Hashimoto’s can also disrupt your sleep patterns, making fatigue worse. 

Learn more about what to do if you are always tired and tips on how to increase energy naturally.

2. Weight gain 

When your thyroid doesn’t produce its hormones in sufficient quantities and your metabolism slows down, you don’t burn off your calories as quickly as you should. 

The result is a gain in weight – usually quite a modest amount, but still enough to affect the way you feel about yourself.

But not all of the weight gain associated with Hashimoto’s and hypothyroidism is down to a slower metabolism. 

It can also be caused by an accumulation of salt and water. This happens when changing hormone levels affect the function of your kidneys.

Learn more about healthy weight loss tips for women, how to lose weight with Hashimoto’s, and how to use clean eating for weight loss.

3. Dry skin 

Dry skin is a pretty common sign that your thyroid hormone levels are low, and may be a sign of a Hashimoto’s flare up.

The increase in dry skin is caused by a decrease in secretions from the eccrine glands – the sweat glands that are located all over your body.

The secretions from these glands – combined with the oils on the surface of your skin – help keep your skin moisturized, hydrated, and supple. 

Without the moisture it needs, your skin can feel very dry and become noticeably flaky. So, dry skin can be a sign of a Hashi’s flare-up.

a woman rubbing a patch of dry skin on her hand.

4. Cold intolerance 

As mentioned earlier, the regulation of your body temperature is one of the many processes influenced by your thyroid hormones. 

Indeed, some people even describe the thyroid gland as a thermostat for the body.

Because a drop in these hormones causes your metabolism to lower, your blood vessels begin to narrow and your skin becomes much more sensitive to the cold. 

If you find yourself layering up when everyone else in the room seems comfortable, it could certainly indicate a Hashimoto’s flare-up.

Some people experiencing low thyroid report that their hands and feet are always cold. If this happens to you, then it might be time to have your thyroid levels checked.

Learn the lab tests that most women need and how to order lab tests online.

5. Hair loss 

It is normal to lose some hair on a daily basis – but if you are noticing yours falling out excessively, Hashimoto’s could be to blame. 

This type of hair loss is usually diffuse, which means that you lose hair from all over the scalp rather than just in spots or patches. 

It happens because the compromised function of your thyroid disrupts your natural hair growth cycle. 

You might also notice hair loss from other parts of your body, including your eyebrows. 

Hair loss can be caused by other factors, too. Long-term fasting (see my article about the dangers of intermittent fasting for women) and low blood iron stores can also cause hair loss and thinning hair.

6. Constipation 

Another of the many bodily systems regulated by the thyroid gland is the digestive system. 

When your thyroid hormone levels are low, your entire system slows down and bowel movements become less frequent. This results in constipation and can be sign of a Hashimoto’s flare-up. 

There is also research to indicate that hypothyroidism is associated with a condition called SIBO – small intestinal bacterial overgrowth. In some cases, this can lead to the production of methane gas, which is another cause of constipation. 

See my Anti-Constipation Smoothie for temporary help in relieving constipation.

a woman holding her stomach.

7. Depression 

Many people experience low moods, sadness, and depression with flare-ups of Hashimoto’s disease. 

But while experts acknowledge a very strong link between thyroid disorders and depression, they have yet to establish the exact cause.

8. Memory problems

Low levels of thyroid hormones can contribute to “brain fog”, making it hard to concentrate and affecting memory. 

Again, researchers aren’t exactly sure why, but it is widely believed that the thyroid hormones play a big part in the areas of the brain responsible for our cognitive skills and memory.

9. Muscle weakness 

Almost 80% of people with thyroid disorders are affected by muscle weakness, usually nearer to the center of the body.

As yet, the link between the two isn’t fully understood. Scientists believe that the main cause is the alteration of fast-twitching type 2 muscle fibers to slow-twitching type 1 fibers in people with thyroid dysfunction.

a man holding his leg.

10. Irregular periods 

Disruptions to your thyroid hormone levels often result in irregular or very light periods. In some cases, periods can stop altogether for several months or more – a condition known as amenorrhea.

There can be other changes, too, including premenstrual spotting and even ovarian cysts.

It’s important to note any disruptions to your menstrual cycle and discuss them with your healthcare provider, as there is a risk that long-term changes could lead to infertility. 

See my related articles on how to eat for your cycle and the best diet for fertility.

11. Hoarseness 

It may sound like an unlikely symptom, but hoarseness can be a strong sign of a Hashimoto’s flare-up. Other changes may also be connected, such as low voice, vocal fatigue, or a reduced range.

Researchers have noted that disorders of the thyroid gland cause minor changes in voice parameters, likely due to the close proximity of the vocal cords to the enlarged thyroid gland.

12. Swelling in the neck 

When the thyroid gland becomes enlarged to a noticeable extent, it is called a goiter. A goiter is one of the most common symptoms of Hashimoto’s disease. 

Not only does your neck look visibly swollen, but it also becomes quite difficult to swallow. 

This enlargement is caused by the overproduction of a hormone called TSH (thyroid stimulating hormone) by the pituitary gland. This hormone (as its name suggests) stimulates the thyroid to produce more hormones and grow in size.

a woman rubbing her neck.

Tips to manage a Hashimoto’s flare-up

Seek medical treatment

Hashimoto’s disease is usually treated with thyroid hormone replacement therapy, typically a synthetic type of T4 called levothyroxine.

Flare-ups of Hashimoto’s can be an indication that your thyroid medication isn’t working effectively or you aren’t taking enough.

This may happen if you are taking another type of medication or a supplement that is affecting how much thyroid medication your body is absorbing. There can be other reasons too.

It is important to discuss this with your healthcare provider as it might mean that your dosage of levothyroxine needs adjusting. Alternatively, you might be advised to take your other medications or supplements at different times of the day.

It’s also important to remember that there are other factors that can impact your thyroid function and the effectiveness of your medication (see below). For that reason, it’s a good idea to get your thyroid levels checked on a regular basis, 

If you are taking the right amount of levothyroxine and absorbing it effectively, you should avoid Hashimoto’s flare-ups in the future. 

a woman having her neck examined by a doctor.

Consider lifestyle changes

While medication is important when dealing with Hashimoto’s disease, making a few changes to your lifestyle can help improve your symptoms too!

First, take a look at your diet and ensure that it is well-balanced and nutritious. Certain nutrients – particularly zinc, selenium, and iodine – are very important for maintaining a healthy thyroid gland. 

Rich sources of zinc and selenium are high-protein foods like meat, fish, nuts, and dairy. 

Good sources of iodine include “iodized” table salt, seaweed, fish, dairy, and eggs. 

But you should discuss your iodine intake with your doctor, as too much iodine can be problematic for people with thyroid disorders

Probiotics can be useful, too. There have been studies highlighting a link between gut bacteria and thyroid function, and it has been noted that people with Hashimoto’s often suffer from an overgrowth of “bad” bacteria. Probiotic foods and supplements help maintain the balance of bacteria in the gut. 

See my articles on the best gut healing foods and the best foods with natural probiotics.

Above all, focus on clean eating!

Autoimmune reactions can be increased by inflammation, so avoiding the foods that cause it is important. This means ditching processed meals and snacks, cutting down on sugar, and consuming more whole, fresh foods.  

See how to eat clean and get the best clean eating recipes for beginners.

Moderate exercise can also be helpful and can help reduce Hashimoto’s symptoms. To ensure you stick with it, choose activities that you enjoy, and that you can easily incorporate into your schedule. These could include walking to work, riding a stationary bike as you watch TV, swimming, or enjoying long walks with your dog.

See my full articles on the best activities for autoimmune disease.


A well-rounded, balanced diet should contain the nutrients you need for a healthy thyroid.

But, if you struggle to meet your goals, or have difficulties absorbing certain nutrients, your healthcare provider may suggest a dietary supplement.

Don’t try going it alone – it’s important to speak to a medical professional before taking supplements. This is to ensure that they won’t interfere with your thyroid medication.

See the best supplements for women over 50 and the best vitamins for women in their 30s.

Cope with symptoms

Another way to help control and manage your symptoms is to keep stress to a minimum.

We often underestimate the impact that stress can have on our bodies, and while it may not be the root cause of a Hashimoto’s flare-up, it can certainly worsen the symptoms. 

In fact, experts found that stress management in women with Hashimoto’s reduced their levels of antithyroglobulin antibodies.

Stress comes in many forms. We can experience physical stress when we are ill or suffer an injury, whereas emotional stress is associated with the worries connected to daily life. 

Life-changing conditions like pregnancy and menopause also put our bodies in a state of stress.

There are several ways in which you can manage stress. These are helpful not just in relieving your symptoms, but also in improving your quality of life overall.

Techniques to try include:

  • Improving the quantity – and quality – of your sleep. This means turning off your screens and devices well before bedtime and perhaps establishing a relaxing night-time routine. This could include a long, hot bath, meditation, or time to read a book.
  • Investing in a few adult coloring books. It’s amazing how relaxing coloring-in actually is!
  • Taking a daily walk outside, preferably in a natural environment.
  • Increasing the amount of (fun) exercise you do – think dancing, or cycling with friends!
  • Maintaining a positive mindset. A great way to do this is to make a list of the 3 best things that happen to you each day.
  • Avoiding unhealthy habits, such as drinking alcohol, smoking, or even relying on too much caffeine. A healthier lifestyle promotes a healthier mind. Try to stick with a healthy diet to reduce chronic inflammation and to support your autoimmune condition.

Hashimoto’s Flare-up Symptoms: Conclusions

Medication can help control Hashimoto’s disease, but there are factors that may affect just how well it works. 

This means that you can experience flare-ups from time to time when you suddenly begin to notice symptoms again. Learning to spot them and seeking medical advice is important, as often a simple adjustment to your dosage is all that’s needed to restore balance. 

The good news is that your symptoms should then resolve within just a few weeks, so you can soon get back to enjoying a happy and healthy lifestyle.

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About the Author: Carrie Forrest has a master’s degree in public health with a specialty in nutrition. She is a top wellness and food blogger with over 5 million annual visitors to her site. Carrie has an incredible story of recovery from chronic illness and is passionate about helping other women transform their health. Send Carrie a message through her contact form.

Note: this post is for informational purposes only and is not intended as medical advice. Please consult your healthcare provider for recommendations related to your individual situation.