Nursing care
Hypocalcaemia vs hypercalcaemia: tetany, weakness and safety precautions
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated October 2026
Short answer
Low calcium makes nerves and muscles overexcitable, causing tingling, cramps, tetany, positive Chvostek and Trousseau signs, and a prolonged QT interval. High calcium dampens excitability, causing weakness, constipation, kidney stones, confusion and a shortened QT interval. Safety for low calcium centres on airway and seizures; for high calcium, on hydration, mobility and falls.
Think excitability: too much or too little
The clearest way to separate the two is the direction of neuromuscular excitability. Low calcium lowers the threshold for nerve firing, so the body becomes twitchy: numbness and tingling around the mouth and in the fingers, muscle cramps, hyperactive reflexes and, in severe cases, tetany, laryngospasm and seizures.
High calcium does the opposite. Nerves and muscles become sluggish, producing fatigue, muscle weakness, reduced reflexes, constipation, nausea and, as levels climb, confusion, stupor and coma. The memory aid of stones, bones, groans and psychiatric overtones captures kidney stones, bone involvement, abdominal symptoms and mental changes. Polyuria and thirst may also appear as the kidneys struggle to concentrate urine.
Use Chvostek, Trousseau and the ECG carefully
Chvostek sign is twitching of the facial muscles when the facial nerve is tapped in front of the ear. Trousseau sign is carpal spasm when a blood pressure cuff is inflated on the upper arm for a few minutes. Both point to low calcium, although a positive Chvostek sign also occurs in some people with normal levels.
On the ECG, hypocalcaemia prolongs the QT interval and hypercalcaemia shortens it. These findings support, rather than replace, the laboratory result. Because much calcium is bound to albumin, a low total calcium in a patient with low albumin may not reflect a true deficit, so an ionised calcium or corrected value may be requested. Interpreting calcium alongside albumin also prevents unnecessary replacement in patients whose active calcium is adequate.
Link each imbalance to its typical causes
Common causes of low calcium include damage to the parathyroid glands during thyroid or neck surgery, vitamin D deficiency, kidney disease, low magnesium and acute pancreatitis. After thyroidectomy, the nurse asks about tingling around the mouth and fingers and keeps emergency equipment available according to local protocol.
High calcium is most often caused by hyperparathyroidism or cancer. Other causes include prolonged immobilisation, thiazide diuretics, excess vitamin D and some granulomatous diseases. A patient with known malignancy who becomes newly confused and constipated is a classic scenario that should prompt a calcium level and escalation.
Apply the safety precautions each needs
For hypocalcaemia, priorities are airway and seizure safety: monitor for stridor or voice change that may signal laryngospasm, implement seizure precautions, and use cardiac monitoring when levels are significantly low. Intravenous calcium is given as prescribed, with care for the infusion site, and extra caution in patients receiving digoxin.
For hypercalcaemia, priorities include hydration and output monitoring as prescribed, encouraging mobility when possible, fall prevention for weakness and confusion, and safe handling when bone disease may make bones fragile. Report signs of kidney stones such as flank pain, and watch for heightened digoxin sensitivity, as high calcium increases toxicity risk.
Work through a hypothetical post-thyroidectomy call
Imagine a hypothetical client the day after a total thyroidectomy who reports tingling around the lips and fingertips, and the nurse notices hand spasm when taking a blood pressure. The options include reassuring the client that this is normal surgical pain, offering an analgesic, or assessing the airway and reporting suspected hypocalcaemia urgently.
Assessing the airway and reporting urgently is the strongest response, because parathyroid injury can cause a rapid fall in calcium with risk of laryngospasm and seizures. The hand spasm during cuff inflation resembles a Trousseau sign. Analgesia does not address the cause, and reassurance delays treatment the prescriber is likely to order. Document the timing and nature of symptoms so the team can track the response to treatment.
Sources and further reading
MSD Manual Professional: Hypocalcemia. Causes including post-thyroidectomy hypoparathyroidism, paresthesias, tetany, laryngospasm, seizures, Chvostek and Trousseau signs, QT prolongation, albumin correction and digoxin caution.
MSD Manual Professional: Hypercalcemia. Hyperparathyroidism, cancer, immobilisation and thiazide causes, constipation, weakness, confusion, stones, shortened QT and increased digoxin sensitivity.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our dosage calculation and lab values practice questions are the closest set to what this page covers.
Common questions
Which ECG change goes with each calcium imbalance?
Low calcium prolongs the QT interval, while high calcium shortens it. ECG findings support the laboratory result and the clinical picture rather than diagnosing the imbalance alone.
Why does albumin matter when interpreting calcium?
A large share of calcium is bound to albumin. When albumin is low, total calcium falls even if active ionised calcium is normal, so a corrected or ionised value may be needed.
Why is immobility linked to high calcium?
Without weight-bearing, bone releases calcium into the blood. Prolonged bed rest is a recognised cause of hypercalcaemia, which is one reason mobility is encouraged when it is safe.
More on dosage calculation and lab values