Magnesium Side Effects | What to Know

Magnesium is the fourth most abundant cation in the human body and a critical cofactor in more than 300 enzyme systems that regulate energy metabolism, neuromuscular function, cardiovascular health, bone integrity, and psychological well-being. Understanding potential Magnesium side effects is an important part of using this mineral wisely.

Nature's Sunshine Magnesium provides nervous system support and assists in a variety of bodily functions. Used by several hundred enzymes in their daily tasks, Magnesium is found in the bones, soft tissues, and blood. It helps metabolize various nutrients such as vitamin C, Phosphorus, potassium, and sodium.

Calcium and Magnesium are nutritional partners and work best when taken together. This formulation comes in 250 mg capsules of Magnesium oxide and Magnesium amino acid chelate in a base of Licorice root, Kelp plant, Peppermint leaves, and White willow bark.

Research suggests that between 56 and 68% of Americans do not obtain enough Magnesium in their diet to meet the recommended daily allowance. As we age, Magnesium absorption and retention can decrease, making supplementation worth considering — but being aware of Magnesium side effects helps you use it safely and confidently.

The most frequently reported Magnesium side effects are gastrointestinal in nature. Magnesium supplements can cause nausea, cramps, and diarrhea. In fact, Magnesium supplements often cause softening of stool and are sometimes used specifically for this purpose.

Side effects usually occur at higher doses and are also more common with inorganic forms of Magnesium, such as Magnesium oxide. One meta-analysis found only minor differences in gastrointestinal disturbances between groups given placebo versus 520 mg Mg/day, but withdrawals were not significantly different between groups. Another meta-analysis found that 3 of 13 studies (at doses of 120–973 mg/day) reported diarrhea that led to study withdrawal.

Extra Magnesium from food is generally safe because the kidneys eliminate excess amounts in urine. Hypermagnesemia — excess Magnesium in the blood — from supplemental intake is rare in individuals with normal kidney function. Signs of a Magnesium overdose can include nausea, diarrhea, low blood pressure, muscle weakness, and fatigue. At very high doses, Magnesium can be fatal, though this risk is substantially elevated primarily in individuals with impaired renal function.

The Tolerable Upper Intake Level (UL) for supplemental Magnesium is 350 milligrams. This UL applies only to Magnesium from dietary supplements and medications and does not include Magnesium found naturally in food and beverages. However, some researchers have noted that data indicate doses above the current UL can be consumed without adverse events, and have suggested that increasing the tolerable upper intake level may be safe.

If you have questions about how Magnesium might affect you personally, our naturopath is available for a free consultation — we're always happy to help you find the right approach.

Beyond digestive Magnesium side effects, it's important to understand that Magnesium and drugs use the same transport and metabolism pathways in the body for intestinal absorption, metabolism, and elimination. This means that when one or more medications are taken, there is always a potential risk of interaction with Magnesium status.

Bisphosphonates

Magnesium-rich supplements or medications can decrease the absorption of oral bisphosphonates, such as alendronate, used to support bone health. Use of Magnesium-rich supplements and oral bisphosphonates should be separated by at least 2 hours.

Tetracycline and Quinolone Antibiotics

Magnesium can form insoluble complexes with tetracyclines as well as quinolone antibiotics such as ciprofloxacin and levofloxacin. The antibiotic should be taken at least 2 hours before or 4–6 hours after Magnesium.

Diuretics

Depending on the type, diuretics can increase or decrease Magnesium in the body. Loop and thiazide diuretics deplete Magnesium through increased urinary excretion, while potassium-sparing diuretics such as amiloride and spironolactone reduce Magnesium loss.

Proton Pump Inhibitors (PPIs)

Prescription PPI drugs, when taken for prolonged periods (typically more than a year), can cause hypomagnesemia. The FDA advises healthcare professionals to consider measuring patients' serum Magnesium levels prior to initiating long-term PPI treatment.

Gabapentin

Magnesium may reduce the absorption of gabapentin by 20%, potentially making it less effective.

Always consult with a healthcare professional before combining Magnesium with any medication. Our naturopath is available for a free consultation if you'd like guidance on timing and compatibility.

Certain groups of people are more likely than others to have Magnesium inadequacy. These include older adults (due to decreased absorption), individuals with gastrointestinal disorders, those with type 2 diabetes, people with alcohol dependence, and individuals on certain long-term medications such as diuretics and PPIs.

The diets of most people in the United States provide less than the recommended amounts of Magnesium. Men older than 70 and teenage girls are most likely to have low intakes. Early signs and symptoms of Magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. As Magnesium deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms can occur.

Research suggests that Magnesium supports several important body systems:

• Nervous system health: Magnesium acts as a natural NMDA receptor antagonist, modulating synaptic transmission and neuronal excitability
• Bone density: Magnesium is an essential cofactor in bone mineral metabolism and is required for vitamin D activation. Observational data from large cohort studies found higher Magnesium intake associated with 2–3% greater bone density in women
• Muscle function: Magnesium is essential for muscle contraction and relaxation. Deficiency is associated with muscle cramps, weakness, and impaired exercise performance

Understanding both the benefits and the potential Magnesium side effects helps you make an informed decision about supplementation.

Take 1 tablet daily with a meal. Taking Magnesium with food may help reduce the likelihood of gastrointestinal Magnesium side effects such as nausea or stomach discomfort.

Each tablet provides 250 mg of Magnesium (as Magnesium oxide and Magnesium amino acid chelate), along with 40 mg of Calcium and 30 mg of Phosphorus. The Recommended Dietary Allowance (RDA) for Magnesium varies by age and sex — 400–420 mg/day for adult men and 310–320 mg/day for adult women — so this supplement can help bridge a dietary gap.

If you're unsure whether Magnesium supplementation is right for you, or if you take any medications that might interact with Magnesium, we encourage you to reach out for a free naturopathic consultation. We're here to help you feel confident in your choices.