A little more eyelid drooping, or legs that suddenly feel harder to move. Trouble chewing or swallowing a meal that normally wouldn’t give you a second thought. A myasthenia gravis (MG) flare-up can show up in different ways, and sometimes the first clue is simply that your usual symptoms feel different.

Learning what tends to trigger flares and recognizing the early warning signs can help you know how to respond and when to contact your healthcare team. This article will explain common myasthenia gravis flare-up triggers, symptoms to watch for, and steps that may help prevent flares.

What Can Trigger a Myasthenia Gravis Flare-Up?

Myasthenia gravis causes muscle weakness because the immune system disrupts communication between nerves and muscles at the neuromuscular junction, where nerves signal muscles to move. Symptoms often become worse with physical activity and improve after rest. Several other factors may also make weakness worse or contribute to an myasthenia gravis flare. These are called triggers.

Not everyone has the same triggers. In some cases, MG symptoms worsen without an obvious cause. Keeping track of when your symptoms change may help you and your healthcare team identify patterns.

Stress

Physical or emotional stress may worsen myasthenia gravis symptoms in some people. Research suggests that higher stress levels may be associated with a greater likelihood of MG relapse. There isn’t one proven explanation for why stress can affect myasthenia gravis.

One MGTeam member reported, “Stress is a major trigger for me. At work, to reduce my stress, I plan a lot. This helps me to prepare and reduce the high stress that comes with periods of high activity.”

Surgery

Surgery and anesthesia may increase the risk of worsening MG symptoms. The effects of surgery, pain, medications, and changes in breathing or muscle function can all require special consideration for someone with myasthenia gravis.

Infection

Infections, particularly respiratory infections, can trigger an MG flare-up. Research suggests that respiratory infections are the most common cause of hospitalizations for people with myasthenia gravis.

Certain Medications

Some medications have been associated with worsening myasthenia gravis, although the evidence and level of risk vary from drug to drug. Medications that patients with myasthenia gravis should avoid or use with caution include:

• Certain antibiotics — Some fluoroquinolones, such as ciprofloxacin and levofloxacin; macrolides, such as azithromycin, erythromycin, and telithromycin; and aminoglycosides, such as gentamicin and tobramycin
• Certain heart and blood pressure medications — Beta-blockers, such as propranolol and metoprolol
• Some antimalarial drugs — Chloroquine and hydroxychloroquine
• Magnesium — Particularly magnesium given through a vein
• Some cancer treatments — Immune checkpoint inhibitors, such as pembrolizumab, nivolumab, and ipilimumab
• Botulinum toxin — Such as Botox

A drug appearing on a cautionary list doesn’t necessarily mean you can never take it. In some situations, a medication may still be the most appropriate treatment.

Heat

Hot weather, hot showers, and other sources of increased body temperature can temporarily worsen symptoms in some people with MG. Higher temperatures can make the already-impaired communication between nerves and muscles less effective, which may increase weakness. Symptoms may improve after the body cools down.

Pregnancy and the Postpartum Period

Myasthenia gravis can follow different patterns during pregnancy. Symptoms may worsen, improve, or remain stable, so pregnancy itself isn’t a predictable MG trigger.

A 2026 systematic review found that the worsening of myasthenic symptoms was most common during the first trimester of pregnancy or postpartum (after delivery).

Autoimmune Thyroid Disease

Autoimmune thyroid disease and myasthenia gravis can occur together. Changes in thyroid hormone levels, including both hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid), have been reported in connection with myasthenia gravis exacerbations. However, evidence that thyroid dysfunction directly triggers myasthenia gravis flares is limited.

If you have both conditions, work with your healthcare teams to treat them appropriately and monitor for changes in MG symptoms.

What About Allergies?

Some research has found an association between allergic diseases and myasthenia gravis. For example, studies have linked conditions such as allergic rhinitis, allergic conjunctivitis, and asthma with an increased likelihood of developing myasthenia gravis. However, this research doesn’t show that exposure to allergens or having an allergic reaction triggers an myasthenia gravis flare in someone who already has the condition.

How Can You Help Prevent Myasthenia Gravis Flare-Ups?

Not every myasthenia gravis flare-up can be prevented. However, understanding your triggers and following your treatment plan may help lower the chance of some exacerbations.

One helpful step is to track your symptoms and possible triggers. Note changes in weakness along with illness, heat exposure, stress, sleep, activities, and medication changes. The Myasthenia Gravis Activities of Daily Living (MG-ADL) scale is an eight-question tool that looks at how MG affects activities such as talking, chewing, swallowing, getting up from a chair, and seeing clearly. Keeping track of your MG-ADL score over time may help you and your healthcare team recognize when symptoms are getting worse.

Other steps you can take include:

• Take myasthenia gravis medications as prescribed — Don’t reduce or stop treatment without talking to your healthcare provider. Reducing or withdrawing myasthenia gravis treatment can contribute to worsening symptoms.
• Check new medications — Tell every healthcare professional who treats you that you have myasthenia gravis. Ask about prescription drugs, over-the-counter medications, and supplements before starting something new.
• Lower your infection risk — Keep recommended vaccinations up to date, and take steps to avoid infections. Routine non-live vaccines are generally considered safe for people with myasthenia gravis, but some people taking medications that suppress the immune system may need to avoid live vaccines.
• Plan ahead for surgery — Make sure your neurology, surgical, and anesthesia teams communicate about your myasthenia gravis and medications before a procedure.
• Stay cool when heat affects your symptoms — Use air conditioning or fans, drink cool fluids, and avoid overheating when possible.
• Build rest into your day — Because myasthenia gravis weakness typically increases with repeated muscle use, pacing activities and resting between demanding tasks may help you manage symptoms.

Learning your own patterns is an important part of living with myasthenia gravis. Consider keeping important medical information and instructions from your healthcare team in an easy-to-find place so you’re prepared if your symptoms worsen.