When people think about minerals essential for life, calcium, sodium, and potassium usually come to mind. Yet, magnesium is just as vital. This essential electrolyte is stored primarily in bones but also found in muscles, soft tissues, and fluids. Magnesium plays a central role in:
- Regulating blood pressure
- Controlling blood sugar
- Supporting muscle contraction and relaxation
- Assisting in nerve transmission
- Facilitating over 300 enzymatic reactions
The normal serum magnesium level is 1.5–2.5 mg/dL. Any deviation from this range can disrupt neuromuscular and cardiovascular function.
Two key imbalances occur:
- Hypermagnesemia: Too much magnesium (>2.5 mg/dL).
- Hypomagnesemia: Too little magnesium (<1.5 mg/dL).
A simple way to remember magnesium’s effect:
“Magnesium is a sedative.”
- Too much (hypermagnesemia) → Sedated, low energy, everything slows down.
- Too little (hypomagnesemia) → Not sedated, everything excites, leading to hyperactivity and irritability.
Hypermagnesemia: Too Much Sedative in the System
Definition
Hypermagnesemia is defined as serum magnesium >2.5 mg/dL, often due to excessive intake or reduced kidney excretion.
Mnemonic for Symptoms: “LOW EVERYTHING aka SEDATED”
- Low energy – drowsiness, lethargy, even coma
- Low heart rate (bradycardia)
- Low blood pressure (hypotension)
- Low respiratory rate (bradypnea, shallow breathing)
- Low reflexes (reduced deep tendon reflexes, DTRs)
- Low bowel sounds – constipation, ileus
In essence, excess magnesium slows down neuromuscular and cardiac activity.
Causes & Risk Factors of Hypermagnesemia
1. Increased Magnesium Intake
- Excessive use of magnesium-containing antacids (TUMS) or laxatives.
- Iatrogenic: Over-administration of IV magnesium (e.g., in eclampsia).
2. Decreased Magnesium Excretion
- Renal insufficiency/failure → kidneys fail to excrete Mg.
- Dehydration or hemoconcentration.
- Diabetic ketoacidosis (DKA): Shifts in electrolyte balance cause magnesium retention.
Clinical Features of Hypermagnesemia
- Neurological: Lethargy, drowsiness, confusion, coma.
- Cardiac: Bradycardia, hypotension, widened QRS, cardiac arrest in severe cases.
- Respiratory: Depressed breathing, shallow respirations due to muscle weakness.
- Musculoskeletal: Diminished reflexes (areflexia), muscle weakness.
- GI: Nausea, vomiting, constipation.
Diagnosis of Hypermagnesemia
- Serum magnesium >2.5 mg/dL.
- ECG: Prolonged PR interval, widened QRS, cardiac conduction block.
- Associated labs: Elevated creatinine in renal insufficiency.
Management of Hypermagnesemia
1. Stop magnesium intake: Discontinue magnesium-containing drugs, laxatives, or IV therapy.2. Enhance excretion:
- Diuretics (loop diuretics with saline infusion).
- Hemodialysis in severe renal failure.
Hypomagnesemia: When the Sedative is Missing
Definition
Hypomagnesemia is defined as serum magnesium <1.5 mg/dL. Because magnesium is closely tied to calcium and potassium, low levels can also cause secondary hypocalcemia and hypokalemia, worsening symptoms.
Mnemonic for Symptoms: “HIGH EVERYTHING aka NOT SEDATED”
- High heart rate (tachycardia)
- High blood pressure (hypertension)
- Increased deep tendon reflexes (hyperreflexia)
- Twitches, paresthesias, cramps
- Tetany and seizures
- Irritability and confusion
- Shallow breathing due to muscle spasms
Classic Clinical Signs (Same as Hypocalcemia)
- Trousseau’s Sign: Carpal spasm with inflated BP cuff.
- Chvostek’s Sign: Facial twitching with tapping.
(Remember: Calcium and magnesium rise and fall together — hypomagnesemia often coexists with hypocalcemia).
Causes & Risk Factors of Hypomagnesemia
1. Insufficient Intake
- Malnutrition, chronic vomiting/diarrhea.
- Alcoholism.
- Malabsorption syndromes (Celiac disease, Crohn’s).
2. Increased Excretion
- Prolonged use of diuretics.
- Chronic alcoholism (renal wasting of Mg).
- Hyperglycemia and insulin administration (drives Mg into cells).
- Sepsis.
Clinical Features of Hypomagnesemia
- Neuromuscular: Tremors, twitches, seizures, hyperreflexia.
- Cardiovascular: Tachycardia, prolonged QT interval, risk of torsades de pointes.
- Respiratory: Shallow breathing, muscle spasms.
- Psychiatric: Depression, irritability, anxiety.
Diagnosis of Hypomagnesemia
- Serum magnesium <1.5 mg/dL.
- ECG: Prolonged QT interval, widened QRS, risk of ventricular arrhythmias.
- Check calcium and potassium (often low simultaneously).
Management of Hypomagnesemia
1. Magnesium supplementation:
- Oral: Magnesium oxide, magnesium citrate.
- IV magnesium sulfate (in severe or symptomatic cases).
2. Correct associated deficiencies:
- Calcium and potassium replacement if needed.
3. Seizure precautions: Initiate safety protocols.
4. Dietary modifications: Encourage foods high in magnesium:
- Nuts, seeds, legumes, green leafy vegetables, whole grains, fish.
Magnesium-Calcium Relationship
Unlike sodium and potassium, magnesium often mirrors calcium levels.
- Low magnesium → Low calcium (hypocalcemia).
- High magnesium → High calcium effects (sedative state).
Thus, patients with magnesium imbalance often require calcium assessment simultaneously.
Complications of Magnesium Imbalance
- Hypermagnesemia: Cardiac arrest, respiratory paralysis, coma.
- Hypomagnesemia: Seizures, life-threatening arrhythmias (torsades de pointes), osteoporosis with chronic deficiency.
- Both conditions significantly increase mortality risk if untreated.
Quick Clinical Comparison Table
| Feature | Hypermagnesemia (>2.5 mg/dL) | Hypomagnesemia (<1.5 mg/dL) |
|---|---|---|
| Mnemonic | LOW everything (sedated) | HIGH everything (not sedated) |
| Cardiac | Bradycardia, hypotension | Tachycardia, hypertension |
| Neurological | Lethargy, coma | Irritability, seizures |
| Reflexes | Hyporeflexia (↓ DTR) | Hyperreflexia (↑ DTR) |
| Respiratory | Shallow, depressed | Shallow, spasms |
| Signs | — | Trousseau’s, Chvostek’s |
| Treatment | Stop Mg, diuretics, Ca IV, dialysis | Mg sulfate IV/PO, seizure precautions |
Frequently Asked Questions (FAQ)
Q1. What is the normal magnesium level in the blood?
The normal range is 1.5–2.5 mg/dL.
Q2. Which patients are most at risk for hypermagnesemia?
Patients with renal failure or those receiving IV magnesium therapy (such as in preeclampsia/eclampsia).
Q3. Can magnesium imbalance cause heart problems?
Yes. Both high and low magnesium can cause arrhythmias, conduction blocks, or cardiac arrest.
Q4. How does alcoholism affect magnesium levels?
Chronic alcoholism increases magnesium excretion by kidneys and decreases absorption, leading to hypomagnesemia.
Q5. What are good dietary sources of magnesium?
Dark leafy greens, nuts, seeds, legumes, fish, bananas, and whole grains.
