Myasthenia gravis (MG) causes fatiguable muscle weakness, which is muscle weakness that gets worse as you repeatedly or continually use the muscle. This type of muscle weakness can also lead to general fatigue.

Many people with MG also experience chronic fatigue that can leave them feeling tired or exhausted even if their muscle weakness is controlled. Fatigue can get in the way of normal daily activities and affect your quality of life.

If you’re experiencing muscle weakness and/or fatigue with myasthenia gravis, it’s important to understand what’s happening in your body. That way, you can have productive conversations with your healthcare team to find the best possible treatment options to manage all your symptoms.

🗳️ Which symptom of myasthenia gravis affects you the most?

Fatigable muscle weakness (weakness with use that gets better with rest)

Muscle weakness (losing strength)

Chronic fatigue

All of these affect me

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What Does Muscle Weakness vs. Fatigue Feel Like With MG?

Muscle weakness and muscle fatigability feel different in the body.

One member described fatigability like this: “When I do too much with my arms or legs, I have instant fatigue. I have to rest and not move a muscle. But most likely I end up having to lay down and sleep.” Another shared, “I get so tired walking more than 10 to 12 feet with my walker. If I sit for a few minutes, I can get going again.”

“When I do too much with my arms or legs, I have instant fatigue. I have to rest and not move a muscle.”

— An MGteam member

In these cases, using the muscle leads to significant fatigue. These people don’t describe their muscles as feeling weak but tired of working and in need of a rest.

Other members report muscle weakness, where their muscles aren’t actually as strong as they used to be. “I have muscle weakness worsening to the point of kinda wobbling as I walk,” one said. Another added, “I’ve noticed a big difference in my strength … before the diagnosis I could do 40 push-ups. Now I’m lucky to get four.”

For people with muscle weakness, the body doesn’t need rest. It has simply lost strength.

Chronic Fatigue With Myasthenia Gravis

Normal fatigue is temporary and may result from lack of sleep or a hard day’s work. Chronic fatigue is long-lasting, and it’s not caused by working too hard. In one study, more than half of participants diagnosed with myasthenia gravis reported symptoms of chronic fatigue.

What does myasthenia gravis fatigue feel like? One MGteam member described it this way: “It’s like I can feel it drain out when I’ve done too much. It leaves my face and lowers out my body. If I don’t lie down, I’ll fall down.”

A study looked at 53 people living with myasthenia gravis. Researchers found that feelings of fatigue weren’t always connected to muscle weakness. This means that you can experience fatigue even if your myasthenia gravis is well controlled or in remission. It also means that sometimes you may need to look beyond muscle weakness to find out what’s causing fatigue.

Some MGteam members experience both kinds of fatigue. “MG has shown me two very different kinds of fatigue,” explained one. “There’s the fatigue of specific muscles — e.g., I can’t hold my phone up very long. And there is the whole-body fatigue that’s not centered in any particular muscle group, a kind of crushing weariness that’s relieved only by a long night’s sleep.”

“There’s the fatigue of specific muscles — e.g., I can’t hold my phone up very long. And there’s the whole-body fatigue … a kind of crushing weariness that’s relieved only by a long night’s sleep.”

— An MGteam member

Related Conditions That Can Cause Fatigue

People who live with myasthenia gravis have a higher risk for certain other health conditions, too. Some of these can also cause fatigue or make fatigue that you’re already experiencing worse.

Depression

People living with myasthenia gravis are more likely to experience depression, even compared to people living with other autoimmune disorders. Significant tiredness and low energy can be symptoms of depression.

If you find yourself feeling sad, hopeless, or extremely irritable, or if you’ve lost interest in things you used to enjoy, talk to your doctor about being screened for depression. There are a variety of treatments that can improve depression, and these may also help with fatigue.

Lupus

MG and systemic lupus erythematosus (SLE, or simply lupus) might be associated. One study looked at a very large database and found that people living with myasthenia gravis were over 10 times more likely to have lupus than those without MG. However, only 1.3 percent of people with lupus develop myasthenia gravis.

Furthermore, it seems that people with myasthenia gravis who underwent thymectomy have a higher chance of developing lupus compared to people with MG who didn’t have thymectomy. Thymectomy is surgery to remove the thymus gland, and it’s necessary in some cases of MG.

It’s important to note that, while there’s an association between having a thymectomy and developing lupus, current research doesn’t prove that this surgery causes lupus.

Fatigue is one common symptom of lupus. Other lupus symptoms include:

If you’re experiencing fatigue along with other potential lupus symptoms, talk to your doctor.

Thyroid Disease

There are a few autoimmune diseases that affect your thyroid, but the one most commonly associated with myasthenia gravis is Graves’ disease (hyperthyroidism). Researchers don’t know exactly how they’re connected. MG is less often associated with Hashimoto thyroiditis, which usually causes hypothyroidism.

In Graves’ disease, the thyroid produces too much thyroid hormone. This is called hyperthyroidism. Fatigue is a common symptom of hyperthyroidism, especially when the condition isn’t being treated.

One MGteam member with both myasthenia gravis and thyroid disease shared, “Fatigue seems related to forgetting thyroid meds or disruptions to schedule that keep me from getting things done. That leads to ‘overwhelm’ and fatigue.”

“Fatigue seems related to forgetting thyroid meds or disruptions to schedule that keep me from getting things done. That leads to ‘overwhelm’ and fatigue.”

— An MGteam member

Besides fatigue, Graves’ disease may cause:

If you notice these symptoms, talk to your medical team about whether you may have a thyroid condition in addition to myasthenia gravis.

Rheumatoid Arthritis

Somewhere between 1 percent and 4 percent of people living with myasthenia gravis also have rheumatoid arthritis (RA). RA causes inflammation in your joints and throughout your body. It can cause issues with your heart, lungs, blood vessels, and more.

Fatigue is a common symptom of RA. It can also cause:

Let your doctor know if you develop joint pain or other potential symptoms of RA.

Talk to Your Doctor About Muscle Weakness and Fatigue

If you’re still experiencing symptoms of myasthenia gravis (which may include drooping eyelids, double vision, and problems swallowing as well as muscle weakness) despite sticking to your treatment plan, it’s important to let your neurology team know.

Fatigue may be directly related to myasthenia gravis or caused or worsened by another health problem. Your doctor may order blood tests to check for signs of other autoimmune conditions.

Your doctor may be able to recommend making changes to your treatment plan that can help. They may suggest changing dosage or medications, adding physical or occupational therapy, or getting other health conditions under control.

Your quality of life is important, and your healthcare team can likely help you find ways to feel your best.