Magnesium Deficiency: Causes, Symptoms, and How to Test

Medically reviewed by Dr. Sarah Mitchell, MD — Internal Medicine

See also: 10 Signs You’re Magnesium Deficient (And What to Do About It) | Best Electrolyte Supplements 2026: Powders, Pills & Drinks Compared

The Hidden Epidemic: Why 50% of People Are Low in Magnesium

Magnesium deficiency is the single most common mineral deficiency in the developed world — yet it’s rarely tested for. Here’s why:

Why Magnesium Deficiency Is So Common

1. Soil Depletion Modern industrial farming has stripped magnesium from topsoil. A 2004 study in the Journal of the American College of Nutrition found that USDA nutrient data for 43 garden crops showed declines of 25-50% in magnesium content between 1940 and 1999.

2. Processed Food Diet Refining grains removes 80-90% of magnesium. White flour, white rice, and sugar — which make up the majority of calories in Western diets — contain virtually no magnesium.

3. Chronic Stress Stress hormones (cortisol, epinephrine) rapidly deplete magnesium. Research shows chronic stress can increase magnesium excretion by 2-3x. This creates a vicious cycle: stress depletes magnesium, and low magnesium increases stress sensitivity.

4. Medications That Deplete Magnesium

• Proton pump inhibitors (PPIs) — omeprazole, pantoprazole, esomeprazole (reduce absorption by 40-60%)
• Diuretics — furosemide, hydrochlorothiazide (increase urinary excretion)
• Metformin — reduces absorption
• Oral contraceptives — increase excretion
• Antibiotics — gentamicin, amphotericin B (increase excretion)

5. Intense Exercise Athletes lose 10-20% of daily magnesium through sweat. Combined with the increased metabolic demands of training, active individuals may need 20-40% more magnesium than sedentary people.

6. Aging Magnesium absorption decreases with age, and urinary excretion increases. Adults over 70 may need 30% more magnesium to maintain adequate levels.

Why Standard Testing Misses 50% of Deficiencies

The most common test — serum magnesium — is notoriously inaccurate:

• Serum contains only 1% of total body magnesium
• The body maintains serum levels by pulling magnesium from bones and tissues
• You can have normal serum magnesium while being severely depleted at the cellular level

Better Tests for Magnesium Status

Recommendation: Ask your doctor for RBC magnesium (not just serum). This measures magnesium inside your red blood cells and is far more reflective of total body status. Normal RBC magnesium is 4.2-6.8 mg/dL.

15 Signs of Magnesium Deficiency

Early/Mild Deficiency

1. Loss of appetite
2. Nausea and vomiting
3. Fatigue and weakness
4. Muscle twitches and cramps (especially eyelids, calves)
5. Difficulty sleeping

Moderate Deficiency

6. Numbness and tingling in extremities
7. Personality changes (irritability, anxiety)
8. Heart palpitations or arrhythmias
9. High blood pressure
10. Migraine headaches

Severe Deficiency

11. Muscle cramps and spasms (tetany)
12. Seizures
13. Coronary artery spasms
14. Hypocalcemia (low calcium — magnesium is required to activate vitamin D)
15. Hypokalemia (low potassium — magnesium regulates potassium channels)

Who Should Get Tested?

• Anyone with symptoms listed above
• People taking PPIs, diuretics, or metformin
• Athletes and people under chronic stress
• Those with osteoporosis or frequent fractures
• People with heart arrhythmias or unexplained hypertension
• Anyone with chronic fatigue or fibromyalgia
• Adults over 60

How to Increase Magnesium Intake

Food Sources (Aim for 200-300mg from diet)

Supplementation Strategy