Magnesium and myasthenia gravis: Potential risks
Last updated April 18, 2025, by Agata Boxe
Fact-checked by Patrícia Silva, PhD
Magnesium is an essential mineral that plays a role in nerve and muscle health, but taking magnesium supplements can potentially worsen myasthenia gravis (MG) symptoms. Supplements should be avoided if you have the disease, and should never be used without talking to your healthcare team.
Often MG is caused by the immune system mistakenly attacking the receptors for acetylcholine, a chemical messenger that helps nerves “talk” to muscles to contract them. The resulting communication problems can lead to muscle weakness and fatigue, which are the main MG symptoms.
It is important to get enough magnesium, but it should be from your diet, such as by eating vegetables such as cooked spinach. Supplements and some medical treatments with magnesium can worsen muscle weakness, cause breathing issues, and interfere with MG treatments.
Role of magnesium in the body
Magnesium helps regulate muscle contractions and relaxation and is involved in nerve-muscle interactions. The mineral acts as a calcium blocker in muscle cells, controlling the levels of calcium.
Calcium supports muscle contraction, while magnesium ensures that only a specific amount of calcium is in the cells. Magnesium allows muscles to relax after contraction, preventing muscle cramps or spasms caused by too much calcium.
Calcium and magnesium impact interactions between nerves and muscles through the minerals’ opposite effects on acetylcholine. While calcium promotes the release of acetylcholine to help muscles contract, magnesium inhibits it, allowing them to relax.
A diet that includes all essential nutrients, including magnesium, will ensure that you are getting the right amount. Food sources are less likely than supplements to lead to excessive levels of one nutrient that might affect your MG symptoms.
Foods that are high in magnesium include:
- almonds
- black beans
- cashews
- chia seeds
- cooked spinach
- edamame
- fortified cereal
- peanuts
- peanut butter
- pumpkin seeds
- soy milk.
If chewing can be an issue, you can blend nuts and seeds in a blender or food processor, then sprinkle them into smoothies and onto salads.
Potential risks of magnesium for myasthenia gravis patients
Taking magnesium supplements has risks. People with MG should avoid them and not use them to treat side effects of MG medications.
The negative effects of magnesium supplements in MG may include worsening muscle weakness, interactions with MG treatments, and an increased risk of respiratory complications.
Intravenous infusions of magnesium that may be given for certain health conditions can also worsen MG symptoms.
Muscle weakness amplification
Taking magnesium with MG may interfere with nerve-muscle communication, contributing to or worsening muscle weakness.
In MG, an autoimmune disorder, the communication between nerves and muscles is already impaired by the immune system’s attack.
Too much magnesium may affect calcium’s muscle-contracting effect. It can also inhibit the release of acetylcholine, which promotes muscle contraction.
The mineral’s effects can consequently decrease muscle strength and worsen MG symptoms.
Impact on medication effectiveness
Magnesium supplements can interfere with MG treatments.
For example, magnesium can interact with anticholinesterase drugs, which slow down the breakdown of acetylcholine. They improve nerve-muscle communication and counteract muscle weakness in MG.
The same MG medications can sometimes cause muscle cramps or twitches. Still, these side effects should not be treated with magnesium supplements despite the mineral’s muscle-relaxing properties.
Magnesium may counteract the drugs’ intended effects — by suppressing the release of acetylcholine — and worsen muscle weakness.
And evidence in the general adult population suggests that it is unlikely that taking magnesium helps alleviate muscle cramps.
Risk of respiratory complications
One of the risks of magnesium in MG is its potential effect on the muscles involved in breathing.
Magnesium may impact respiratory muscles, making it difficult to breathe. These muscles in people with MG are already affected by the disease, and supplementation could further decrease their strength.
In rare cases, taking magnesium without medical supervision can even trigger myasthenic crisis, a serious, life-threatening breathing issue that requires immediate emergency care.
Treatment involves ventilation, either by inserting a tube into the airways and connecting it to a machine or delivering oxygen through a mask.
If you ever think you are experiencing a myasthenic crisis, call 911.
Current research on magnesium and myasthenia gravis
Research confirms the link between magnesium and MG complications, especially with intravenous treatments.
Single-case reports of people with MG have described myasthenic crisis or acute respiratory failure, a serious health emergency that makes it difficult to breathe, after treatment with intravenous magnesium sulfate.
A 2023 review of electronic health records found that administration of intravenous magnesium sulfate in people with MG was linked to respiratory issues.
MG is also one of the contraindications for magnesium sulfate use in pregnant women. This treatment is often for those with high blood pressure and eclampsia, which are seizures associated with pregnancy.
Not all healthcare providers know about the effects of magnesium on MG, especially if they are not MG specialists. It is extremely important that you tell or remind your doctor when making treatment decisions.
It is ultimately up to your doctor to weigh the risks and benefits of all treatments, including those involving magnesium, and decide which ones may be most appropriate for your specific case.
When to consult a healthcare provider
Supplements should only be taken if prescribed by your healthcare provider who is treating you for MG. They may otherwise negatively impact your MG symptoms and interact with MG medications.
If you experience muscle cramps or twitches while taking MG medication, do not self-medicate with magnesium.
Instead, report the issues to your neurologist, who can determine whether it is your medication, the disease itself, or something else causing them. Your doctor may choose to adjust your MG medication dose or prescribe a different treatment.
If you are currently taking magnesium supplements without prior medical consultation, you should notify your doctor about it as soon as possible. You should never start taking magnesium or any other supplements without consulting a healthcare provider.
Myasthenia Gravis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
