A blood test is needed to diagnose a magnesium deficiency, but some potential signs include loss of appetite, nausea, vomiting, fatigue, restless leg syndrome, and poor nail growth. In cases where a true deficiency is found, doctors are likely to recommend a magnesium supplement.
Certain health conditions, such as alcoholism, and certain medications, such as tetracycline antibiotics for acne, can lower our magnesium levels. Excessive sweating, heavy menstrual cycles, and certain lifestyle factors such as drinking too much caffeine and soda can also lower magnesium levels.
But if a magnesium deficiency is rare, what’s going on with the almost half of adults who the NIH says are getting less than their recommended daily dose? Those people likely fall into the less concerning “insufficient,” rather than “deficient,” category. “While the NIH notes that true magnesium deficiency is rare, there can still be instances where magnesium levels are insufficient,” says Dr. Sekhon. “Someone may benefit from magnesium supplementation if their dietary intake is low or if they experience symptoms like muscle cramps, fatigue, irregular heartbeat, which can suggest magnesium insufficiency even without a diagnosed deficiency.” If you’re experiencing more extreme symptoms, such as severe muscle cramps, seizures, or abnormal heart rhythms, consult a doctor immediately.
“Magnesium can be a very effective supplement,” says Elizabeth Sharp, MD, IFMCP, board-certified medicine physician and founder of Health Meets Wellness. “The key is making sure you’re taking the correct form, preparation, and dosage for the symptoms you’re treating.”
Are there any downsides to magnesium?
Unless you’re allergic to the magnesium-rich foods we’ve mentioned, ingesting the mineral through whole foods should be generally safe. Experts do caution against ingesting the mineral in higher doses (anything above 400 mgs if you’re between the ages of 19 and 31, or above 420 mgs if you’re older than 31), especially in supplements, as that may cause adverse effects, such as nausea and vomiting, diarrhea, lethargy, muscle weakness, dizziness, low blood pressure, slow reflexes, and a slow heart rate.
Dr. Sekhon says those with kidney disease should avoid magnesium supplements because their kidneys won’t be able to effectively remove any excess of the mineral. She also warns that magnesium can interact with certain medications, such as antibiotics and water pills, and it may reduce their effectiveness.
Regardless of your health, you should be mindful about adding supplements. Because supplements are unregulated, you might be taking one that won’t have much—if any—magnesium at all. Or worse, it might be filled with other ingredients you weren’t planning on ingesting that, in extreme cases, could be harmful to your health.
How to safely take magnesium
First and foremost, give your doctor a ring. “Generally, adding magnesium-rich foods like fish and almonds to your diet is harmless,” Keatley says, but she stresses that you should always talk to your doctor before starting (or changing) a supplementation routine. Gannon agrees, adding, “Your best bet is to talk with your doctor if you’re thinking [magnesium supplements] could help you.”