Pharmacology · Electrolytes and rehydration solutions

Calcium gluconate !

IV calcium for acute symptomatic hypocalcaemia. It also protects the heart in severe hyperkalaemia and reverses magnesium toxicity.

Updated 2026-11-01

Class: Electrolytes and rehydration solutions
Target: Calcium ions: membranes of heart, nerve and muscle (no single receptor)
ATC code: A12AA03
WHO Model List of Essential Medicines

Mechanism of action

Calcium gluconate releases calcium ions into the blood, restoring the calcium needed for nerve conduction, muscle contraction and clotting, and relieving tetany. In hyperkalaemia, extra calcium raises the threshold potential of heart cells and restores the gap to the resting potential, which stabilises the membrane while other treatments lower potassium. It also opposes magnesium's effects at the nerve terminal.

IV calcium gluconate releases free calcium ions
Low calcium is corrected: tetany and spasms ease
In hyperkalaemia it stabilises the heart cell membrane
It counteracts the effects of magnesium toxicity

Pharmacokinetics

Distribution: Calcium enters the extracellular fluid and is used for nerves, muscle, clotting and bone

Indications

Acute symptomatic hypocalcaemia (tetany, spasms, seizures)
Protection of the heart in severe hyperkalaemia
Magnesium toxicity, for example during treatment of pre-eclampsia Preeclampsia →

Adverse effects

Common

Local inflammation and pain at the injection site
Tingling and a warm feeling
Flushing and low blood pressure with fast injection
Chalky taste

Contraindications

Hypercalcaemia
Newborns (28 days or younger) receiving IV ceftriaxone

Key interactions

Digoxin and other cardiac glycosides: Arrhythmias; high calcium increases digoxin toxicity
Ceftriaxone: Calcium-ceftriaxone precipitate; never in the same line, and contraindicated in newborns
Solutions containing bicarbonate or phosphate: Precipitation in the line
Thiazides, vitamin D or vitamin A: Higher risk of hypercalcaemia
Minocycline injection: Calcium binds it and inactivates it

What is monitored

Serum calcium (total and, ideally, ionised) during therapy
ECG and heart rate during injection
Infusion site
Kidney function

Administration and safety

Given IV only, slowly or as an infusion and diluted as the product label states; rapid injection can cause low blood pressure, bradycardia and cardiac arrest.
Use a secure, well-running vein (ideally large); extravasation causes necrosis and calcinosis. Stop the infusion at once if it leaks.
Never mix with bicarbonate, phosphate or ceftriaxone; flush the line well between ceftriaxone and calcium in patients older than 28 days.
Look-alike risk: calcium gluconate and calcium chloride contain very different amounts of calcium and are not interchangeable one-for-one.

Nursing care

Before giving: check serum calcium, heart rhythm and whether the patient takes digoxin.
Monitor the ECG and heart rate during injection; stop and report bradycardia or chest discomfort.
Check the injection site often for redness, swelling or pain.
Watch for signs of high calcium: nausea, weakness, confusion, constipation.
Check for Chvostek or Trousseau signs and tingling to judge the response in hypocalcaemia.

Pregnancy and breastfeeding

Data are limited; untreated low calcium in pregnancy carries risks for mother and baby, so it is used when needed.

Test yourself

Think of the answer, then tap the question to see it.

How does IV calcium help in severe hyperkalaemia?

It stabilises the heart cell membrane by raising the threshold potential; it does not lower serum potassium, so other treatments are still needed.

Why is calcium never mixed with ceftriaxone?

They form a calcium-ceftriaxone precipitate; in newborns this caused fatal deposits in the lungs and kidneys.

What can happen if calcium gluconate is injected too fast?

Vasodilation, low blood pressure, bradycardia, arrhythmias, syncope and even cardiac arrest.

Which drug's toxicity is increased by high calcium?

Digoxin and other cardiac glycosides; arrhythmias can occur when they are given together.

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Preeclampsia

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - CALCIUM GLUCONATE injection, solution (DailyMed (U.S. National Library of Medicine), 2025); Calcium Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); DailyMed - POTASSIUM CHLORIDE tablet, extended release (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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