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what causes low magnesium levels

Low magnesium levels (hypomagnesemia) usually happen because you’re not getting enough magnesium, your gut isn’t absorbing it properly, or your kidneys are losing too much of it.

Main causes at a glance

The big picture: most cases trace back to one (or a mix) of these:

  • Not eating enough magnesium-rich foods over time.
  • Digestive problems that block absorption in the intestines.
  • Kidney-related losses and some hormone problems that increase magnesium loss in urine.
  • Long-term use of certain medications (like diuretics and some acid-reflux drugs).
  • Chronic alcohol use, long-standing diarrhea, or vomiting.
  • Uncontrolled diabetes or anything causing excessive urination.
  • Rare inherited (genetic) kidney tubule disorders.

Think of it as: too little in, too much out, or broken handling in the middle.

1. Low intake and diet patterns

Low intake usually develops slowly but is extremely common in modern diets.

  • Diets low in whole grains, nuts, seeds, legumes, and leafy greens reduce magnesium intake.
  • Highly processed and refined foods are typically poor in magnesium even if calories are high.
  • Older adults, people with poor appetite, food insecurity, or very restrictive diets are at higher risk.
  • Eating enough calories does not guarantee adequate magnesium; diet quality is what matters.

Example: A person living on white bread, sugary drinks, and fast food can be overweight yet still magnesium-deficient.

2. Gut (digestive) problems and surgeries

If your intestines are inflamed, shortened, or moving things through too fast, magnesium doesn’t get enough time to be absorbed. Key gut-related causes:

  • Chronic diarrhea from conditions like Crohn’s disease or ulcerative colitis.
  • Celiac disease and other malabsorption syndromes that damage the small intestine.
  • Long-term vomiting, which leads to both loss of fluids and poor intake.
  • Pancreatitis and some critical illnesses affecting digestion.
  • Bariatric or gastric bypass surgery, which reduces the effective surface area for absorption.

People with long-standing digestive issues often need their magnesium checked regularly.

3. Kidney-related magnesium loss

Healthy kidneys normally “recycle” most magnesium, but some conditions and drugs make them waste it. Situations where kidneys lose excess magnesium:

  • Uncontrolled type 2 diabetes with high blood sugar, causing excessive urination (polyuria).
  • Recovery from some forms of acute kidney injury, when urine output is temporarily very high.
  • Chronic kidney tubule problems, including specific inherited tubule disorders.
  • Hyperaldosteronism (too much aldosterone hormone), which increases salt and water handling and can drag magnesium with it.

In these cases, even a good diet might not fix low magnesium alone because the kidneys are losing too much.

4. Medications that lower magnesium

Several commonly used medications can gradually drive magnesium levels down, especially if taken long term. Important examples:

  • Diuretics (“water pills”) such as loop and thiazide diuretics, used for blood pressure or heart failure, increase urinary magnesium loss.
  • Certain proton pump inhibitors (PPIs) used for acid reflux and heartburn have been linked to reduced magnesium absorption with prolonged use.
  • Some chemotherapy agents and immunosuppressive drugs (e.g., cisplatin, certain calcineurin inhibitors) can cause kidney magnesium wasting.
  • Certain antibiotics (like aminoglycosides) may also lead to increased renal magnesium loss.

Often, the combination of medication plus a marginal diet is what pushes levels into the low range.

5. Alcohol, burns, and other medical conditions

A number of systemic conditions can push magnesium levels down. Common ones include:

  • Chronic alcohol use disorder: reduces intake, damages the gut, and alters kidney handling of magnesium.
  • Large burns: cause fluid shifts and loss of electrolytes, including magnesium.
  • Prolonged critical illness or starvation, including cancer-related poor intake.
  • “Hungry bone” syndrome after parathyroid or thyroid surgery, where healing bone actively takes up magnesium from the blood.

These often occur in hospital or intensive-care settings, where magnesium is monitored closely.

6. Genetic (inherited) causes

Rare, but important when low magnesium is severe and starts young.

  • Gitelman syndrome: a genetic defect in a kidney transporter that causes magnesium and potassium wasting and low blood pressure.
  • EAST/SeSAME syndrome: linked to mutations in a kidney potassium channel, leading to hypomagnesemia and other electrolyte imbalances.
  • Other rare inherited tubulopathies that specifically impair magnesium reabsorption in the kidney.

These conditions usually require specialist evaluation and lifelong management.

7. How low magnesium shows up (and why it matters)

Even though you asked about causes, knowing what to watch for can be helpful. Possible effects:

  • Early or mild: fatigue, low appetite, nausea, muscle twitching, or cramps.
  • More pronounced: tingling, tremors, muscle spasms (tetany), abnormal heart rhythms, mood changes.
  • Often, hypomagnesemia travels with low potassium and low calcium, which can worsen symptoms.

Because mild deficiency can be silent, it’s sometimes only caught on blood tests done for other reasons.

8. When to worry and what to do

Low magnesium is treatable, but the cause must also be fixed or managed. You should seek medical advice if:

  • You have unexplained muscle cramps, tremors, or heart palpitations, especially if you have risk factors like diabetes, digestive disease, or high alcohol use.
  • You’re on long-term diuretics or acid-reflux medications and feel unusually tired, weak, or “off.”
  • You have chronic diarrhea or a condition like Crohn’s or celiac disease.

A clinician can order blood tests, review medications, and decide whether you need dietary changes, oral supplements, or in some cases intravenous magnesium.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.

If you tell me a bit about your health situation (medications, conditions like diabetes or gut issues), I can help you map which of these causes might be most relevant for you (not as a diagnosis, but as a guide for what to discuss with your clinician).