Your left eyelid has been flickering since morning, and by the afternoon meeting it still won’t stop. The night before, your calf knotted up hard at nearly three in the morning, and you had to sit bolt upright and pull your toes back toward you for a while before it eased. When you lay back down you couldn’t get back to sleep, your mind still running over unfinished work.
Some people have already looked into it, suspected a magnesium deficiency, had a blood test and come home with a report that says “within normal limits.” That number is correct. The catch is that a blood test measures only a very small part of the body’s magnesium, so at the clinic the doctor reads it together with your history and muscle testing.
What magnesium does in muscles and nerves
Magnesium is a mineral the body needs every day and has to get from food. In muscles and nerves, magnesium helps muscle fibers relax after each contraction and keeps nerve signals from becoming overexcited. When it runs short, muscles cramp, twitch and spasm more easily, and you may feel restless and find it hard to unwind.
Magnesium has another role that few people notice: it takes part in regulating the stress response. In the review by Pickering et al. (2020), magnesium acts as a brake, helping the body avoid overreacting to pressure.
Even so, twitching, cramps or poor sleep are not necessarily caused by a lack of magnesium. Lack of sleep, overexertion, dehydration, side effects of medicines, thyroid disease and nerve disorders can all cause them.
Why you can still be low with normal blood magnesium
More than 99% of the body’s magnesium sits inside the cells. DiNicolantonio, O’Keefe and Wilson (2018) build on this point of physiology when they discuss people who are low in magnesium without a test showing it. A serum magnesium test measures only the small portion circulating in the blood, and according to the authors, that portion does not reflect magnesium inside the cells, so most cases of magnesium deficiency go undiagnosed. They argue that this silent kind of deficiency contributes to cardiovascular disease and is common enough to be considered a public health problem.
A normal result is still meaningful within its own scope. At the time the sample was taken, your blood magnesium was within limits, so you are unlikely to have a clearly low blood magnesium that needs prompt treatment. Whether there is enough or too little inside the cells is a question this test cannot yet answer.
Stress and magnesium affect each other
In people under psychological stress, magnesium is often low. Pickering et al. (2020) pulled together the research on the two and revisited the idea of a “vicious circle.” Stress makes the body lose magnesium. With too little magnesium, the brake mentioned above weakens, the body becomes more easily stressed, and the next round drains still more magnesium.
Peak season at work is an easy example to picture. Little sleep, rushed meals, and the eyelid starts to twitch. At night it is hard to fall asleep, you wake up more tired, and the next day you handle pressure a little less well.
So even if you really are short of magnesium, a magnesium tablet only undoes one link of that circle. The rest is taking care of your sleep, your meals and the pace of your work; how stress gets into the body is described in our article Normal test results but still tired, in pain and sleepless: how stress affects you.
Who runs low on magnesium without knowing it
The review by DiNicolantonio (2018) lists a few very ordinary reasons why magnesium gradually runs low:
- Eating a lot of refined foods such as polished white rice, white bread and processed foods;
- Taking certain medicines over a long period;
- Having a chronic illness;
- Farm soil that is poor in magnesium, a reason beyond any one person’s control.
Pickering (2020) adds people living with long-term stress, that is, anyone caught in the vicious circle described in the section above. If you take medicines long term, write down their names so the doctor can check whether they affect your magnesium.
How the clinic checks magnesium
At Tam Duc, the question “am I low in magnesium?” is placed within the whole consultation. The doctor asks about your sleep, meals, stress level, the medicines you take and any other conditions you have, and does a clinical examination by modern medicine and by the four examinations of traditional medicine (looking, listening, asking, taking the pulse). Twitching and cramps can come from structure, chemistry or mind; magnesium belongs to the chemical side. When needed, the doctor suggests a blood test that includes magnesium and kidney function.
Alongside lab tests, and even when blood magnesium is already normal, the doctor uses Applied Kinesiology (AK) to check ions, that is, minerals and electrolytes. The doctor has you taste or smell the substance being checked, then tests the muscle again and compares it with before (Walther, 1981, pp. 45–50); how the testing works is explained in our article Why the doctor tests muscles. Magnesium is looked at together with calcium and potassium, because these substances all take part in how muscles work. If there are signs that you are caught in the stress circle, the doctor also checks for stress in the frontal lobe, the limbic system and the cingulate gyrus.
Muscle testing is one part of the consultation, placed alongside the history and the clinical examination, and lab tests are still needed when the doctor suggests them. The numbers in your blood, plus the way your body responds during muscle testing, help the doctor decide with more confidence whether to supplement yet, in what form, or whether the cause has to be looked for somewhere else.
Traditional medicine says “the Liver governs the sinews” (肝主筋, gān zhǔ jīn), meaning that tendons and muscles are nourished by Liver blood. People who often have twitching, cramps at night, light broken sleep and a short temper are usually looked at closely for the Liver and the Heart. Depending on the pattern, the approach may include an herbal decoction modified for each person, acupuncture, and adjustments to nutrition and micronutrients.
Magnesium from everyday meals
White rice is now the everyday staple in most homes. When rice is polished white, most of the bran layer that holds many minerals is removed; the hand-pounded rice of the old days kept a creamy trace of bran and so held on to more.
To get more magnesium from your meals, you can rely on four familiar groups:
- Dark leafy greens such as amaranth greens, spinach and mustard greens;
- Nuts and seeds such as sesame, pumpkin seeds, cashews and peanuts;
- Beans such as black beans, mung beans, soybeans and tofu;
- Whole grains such as brown rice, oats and whole-wheat bread.
There is no need to change everything at once. Mixing a little brown rice into the rice pot, or swapping the afternoon packet of sweet biscuits for a handful of nuts, is already a start.
Magnesium tablets, with or without B6
Pharmacies carry many magnesium products, including some combined with vitamin B6, so many people come to the clinic already asking “should I take magnesium B6?” Supplements help when the body is truly short. Which form, whether B6 needs to come with it and how long to take it are decisions the doctor makes after examining you and reviewing your lab tests and the list of medicines you take. We do not give a dose here, because the right dose differs from person to person.
The kidneys are where magnesium is cleared from the body. People with kidney disease, or who have ever had abnormal kidney function results, should not take magnesium on their own, because magnesium can build up in the blood. People on long-term medicines should also ask the doctor how far apart to space the magnesium tablet and their other medicines.
When to see a doctor right away
You should see a doctor soon, or go to an emergency department, if you have any of the following signs:
- A fast or irregular heartbeat, or palpitations together with dizziness or shortness of breath;
- Severe muscle weakness, difficulty standing up, difficulty gripping objects;
- A seizure, even just once;
- Twitching that spreads over half of the face, or comes with a drooping eyelid or a drooping mouth;
- Cramps together with swollen legs or passing little urine, or cramps that happen while you have kidney disease or ongoing diarrhea or vomiting.
Common questions
Is an eyelid twitch lasting a few days caused by low magnesium?
It can be, but it is more often seen after days of too little sleep, a lot of screen time and stress. Most cases go away on their own with rest. If the twitching lasts for several weeks or comes with any of the signs in the section above, you should see a doctor.
Does muscle testing hurt, and how do I prepare?
Muscle testing does not hurt. You hold a position and the doctor presses gently to see how the muscle responds. How to prepare is covered in our article What to bring and how to prepare for an Applied Kinesiology examination.
Worth keeping
- For one to two weeks, keep a note of your sleep times, each episode of twitching or cramps, and your stress level during the day;
- Keep all your old lab results, including normal magnesium results, to bring to your visit;
- Take photos of the labels of the medicines and supplements you are taking;
- Mix some brown rice into your rice pot, and add dark leafy greens to every main meal;
- Do not take magnesium tablets long term on your own, especially if you have kidney disease;
- Walk or do some light exercise regularly every day;
- Allow about 30–45 minutes for your first visit.
If the twitching and cramps are still going on after a few weeks, you should see a doctor and bring the results you already have. The doctor will look at them together with your sleep, meals, stress level and muscle-testing results before discussing whether to supplement. How the clinic combines its methods is described on our Treatment methods page.
References
- DiNicolantonio JJ, O’Keefe JH, Wilson W (2018). Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis. Open Heart 5(1):e000668. https://doi.org/10.1136/openhrt-2017-000668;
- Pickering G, Mazur A, Trousselard M et al. (2020). Magnesium Status and Stress: The Vicious Circle Concept Revisited. Nutrients 12(12):3672. https://doi.org/10.3390/nu12123672;
- Walther DS (1981). Applied Kinesiology, Volume I – Basic Procedures and Muscle Testing. Pueblo: Systems DC. Chapter Chemical and Nutrition Testing, pp. 45–50.
