Magnesium deficiency stems from three broad problems: not getting enough from food, not absorbing what you eat, or losing too much through your kidneys. Often, more than one of these is happening at the same time. Adults need between 310 and 420 mg of magnesium daily depending on age and sex, and falling short over time can quietly drain your body’s reserves.
How Your Body Manages Magnesium
Understanding why deficiency happens starts with how your body handles magnesium in the first place. You absorb it mainly in the small intestine through two routes: an active transport system that pulls magnesium in when levels are low, and a passive pathway that lets it flow through when there’s plenty available. Together, these create a flexible system that adjusts to how much magnesium is in your gut at any given time.
Your kidneys are the other major control point. About 80% of the magnesium in your blood gets filtered through the kidneys, and more than 95% of that is reabsorbed back into the body. The final stretch of this reabsorption happens in a specific part of the kidney tubule, and whatever isn’t reclaimed there leaves in your urine. Anything that disrupts absorption in the gut or reabsorption in the kidneys can push you toward deficiency.
Digestive Disorders That Block Absorption
Conditions that damage or inflame the lining of your intestines can severely limit how much magnesium you take in. Celiac disease, which causes an immune reaction to gluten that flattens the absorptive surface of the small intestine, impairs the uptake of most nutrients, magnesium included. Crohn’s disease works similarly, creating patches of chronic inflammation that interfere with normal absorption. If sections of the small intestine have been surgically removed, you lose absorptive surface area permanently.
Chronic diarrhea from any cause also matters. Magnesium that would normally be absorbed further along the digestive tract gets flushed out before your body can use it. People with irritable bowel conditions, infections, or any illness that speeds transit through the gut are at higher risk. Even fat malabsorption can play a role: unabsorbed fats in the intestine can trap minerals, including magnesium, and carry them out of the body.
Medications That Deplete Magnesium
Several widely prescribed drug classes lower magnesium levels, sometimes significantly.
Proton pump inhibitors (PPIs) like omeprazole and lansoprazole are among the most common culprits. These acid-reducing drugs, often taken long-term for heartburn or reflux, appear to disrupt the active transport channels that pull magnesium through the intestinal wall. The likely mechanism: by raising the concentration of protons in the intestinal lumen, PPIs change the shape of the channel proteins that bind magnesium, reducing their ability to grab and transport it. The passive absorption route stays intact, but it can’t fully compensate.
Diuretics are the other major category. Loop diuretics and thiazide diuretics both increase magnesium loss through the kidneys, though by slightly different pathways. Both types work by blocking sodium reabsorption in the kidney, which disrupts the electrical gradients that magnesium transport depends on. The result is that more magnesium passes into the urine instead of being reclaimed. Potassium-sparing diuretics can also affect magnesium handling, though typically to a lesser degree.
Other medications linked to magnesium loss include certain antibiotics, some chemotherapy drugs, and immunosuppressants used after organ transplants.
Alcohol Use
Chronic alcohol consumption is one of the most potent drivers of magnesium deficiency. Up to 30% of people with alcohol use disorder have low magnesium levels. Alcohol causes direct dysfunction in the kidney tubules, making them leak magnesium into the urine instead of reabsorbing it properly. On top of that, heavy drinkers tend to eat poorly, taking in less magnesium from food to begin with.
The good news is that the kidney damage from alcohol appears to be reversible. Studies have shown that the tubular dysfunction corrects itself within about four weeks of abstinence, allowing the kidneys to start conserving magnesium normally again.
Diabetes and Insulin Resistance
Type 2 diabetes creates a particularly frustrating cycle with magnesium. Insulin resistance in kidney tissue directly inhibits magnesium reabsorption, causing the kidneys to waste it in urine. High blood sugar makes this worse: when excess glucose spills into the urine, it pulls water and minerals along with it, including magnesium. So the same metabolic problems that define diabetes also actively drain one of the minerals the body needs to manage blood sugar effectively.
Not Enough in Your Diet
Even without any medical condition, many people simply don’t eat enough magnesium-rich food. The recommended daily amount is 420 mg for men over 30 and 320 mg for women over 30. Younger adults need slightly less (400 mg for men 19 to 30, 310 mg for women in that range), while pregnant women need 350 to 360 mg.
Diets heavy in processed foods are the most common dietary cause. Refining grains strips out magnesium along with the bran and germ. A diet built around white bread, packaged snacks, and fast food can easily fall 100 to 200 mg short of the daily target.
Even people who eat whole foods can run into trouble. Long-term studies have found a 20 to 30% decline in the magnesium content of fruits and vegetables over the past several decades, with newer crop varieties tending to contain less magnesium than older ones. Staple grains like wheat, rice, and maize have followed the same trend. So even a “good” diet today may deliver less magnesium than the same diet would have a generation ago.
Foods That Interfere With Absorption
Some otherwise healthy foods contain compounds that reduce how much magnesium your body can actually use. Phytic acid, found in whole grains, seeds, legumes, and some nuts, binds to magnesium in the gut and prevents it from being absorbed. This doesn’t mean you should avoid these foods, as they’re valuable sources of other nutrients. But if your diet leans heavily on unprocessed grains and legumes without much variety, phytates could be limiting your effective magnesium intake.
Oxalates, concentrated in spinach, Swiss chard, beets, almonds, and tea, primarily bind calcium rather than magnesium. But because calcium and magnesium share some absorption pathways, high-oxalate diets can indirectly affect magnesium status. Soaking, sprouting, or fermenting high-phytate foods reduces their phytic acid content substantially, which improves mineral availability.
Other Risk Factors
Age works against you. Older adults absorb less magnesium from food, and kidney function naturally declines with age, reducing the body’s ability to conserve what it has. Combine that with the medications that many older adults take, particularly diuretics and PPIs, and the risk compounds quickly.
Intense or prolonged sweating from exercise or heat exposure increases magnesium losses through the skin. Athletes and people who work in hot environments may need more than the standard recommendations. Chronic stress also appears to increase magnesium excretion, though the exact mechanism is less well defined than for the other causes listed here.
Pregnancy raises magnesium requirements because the mineral is needed for fetal development. Women who enter pregnancy with borderline magnesium levels can tip into deficiency without dietary adjustments. The recommended intake during pregnancy ranges from 350 to 400 mg daily depending on age.
How Deficiency Shows Up
Mild deficiency often produces no obvious symptoms, which is part of what makes it so common. As levels drop further, early signs include muscle cramps, twitching, and fatigue. More significant depletion can cause numbness or tingling in the hands and feet, muscle spasms in the hands or feet (sometimes called carpopedal spasm), and changes in heart rhythm. Symptoms may not appear until serum magnesium falls below 1.2 mg/dL, well below the normal range.
Because magnesium is involved in hundreds of enzyme reactions throughout the body, prolonged deficiency can also affect bone density, blood sugar regulation, and blood pressure. It tends to pull other minerals down with it: low magnesium makes it harder for your body to maintain normal potassium and calcium levels, which can create overlapping symptoms that are difficult to untangle without blood testing.