Physiological adaptation
Potassium, sodium, calcium and magnesium: what to notice and what to report
The signs of too little and too much for the four electrolytes the exam asks about most, and the safety rules for giving potassium.
8 min read·foundation·
Reviewed by a licensed nurse · 25 October 2026
Signs to recognize
| Electrolyte | Too low | Too high |
|---|---|---|
| Potassium (3.5 to 5.0 mEq/L) | Muscle weakness, leg cramps, constipation, shallow breathing, irregular heartbeat | Muscle weakness, nausea, slow or irregular pulse, peaked T waves |
| Sodium (135 to 145 mEq/L) | Headache, confusion, nausea, seizures | Thirst, dry sticky mucous membranes, restlessness, agitation |
| Calcium (about 8.6 to 10.2 mg/dL) | Tingling around the mouth and fingers, muscle spasms, positive Chvostek and Trousseau signs | Weakness, constipation, kidney stones, confusion |
| Magnesium (about 1.7 to 2.2 mg/dL) | Tremor, twitching, hyperactive reflexes, irregular heartbeat | Loss of deep tendon reflexes first, low blood pressure, slow breathing |
Reference ranges vary slightly between laboratories. Use the range printed on the result.
Who is at risk
- ·Low potassium: diuretics, vomiting, diarrhea, insulin, poor intake.
- ·High potassium: kidney failure, potassium-sparing diuretics, ACE inhibitors, burns and crush injuries.
- ·Low sodium: excess water, diuretics, heart failure, SIADH.
- ·High sodium: dehydration, diabetes insipidus, too much salt.
- ·Low calcium: thyroid or parathyroid surgery, low vitamin D, pancreatitis.
Check yourself
Did it stick?
1. A client taking a loop diuretic reports leg cramps and weakness, and the pulse is irregular. Which result is most likely?
2. Which finding suggests hypocalcemia?
3. The client is to receive potassium chloride intravenously. Which action by the nurse is correct?
Sources
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Educational content for exam preparation. It is not clinical guidance and does not replace your facility's policies, current professional guidelines or the advice of a qualified clinician.