Calcium gluconate: dosage, uses, side effects

Calcium gluconate is an injectable form of calcium that’s mainly used in hospitals to quickly reverse low calcium levels or to support heart function during cardiac emergencies. Less commonly, it is also found as an ingredient in over-the-counter mineral supplements.

Read on to learn more about how calcium gluconate works, its side effects, uses, and more.

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Calcium comes in different forms called calcium salts. Each type of calcium salt contains varied amounts of calcium and produces different effects in the body (NIH, 2021). 

Certain calcium salts are found as ingredients in medicines. A few examples are calcium carbonate, an antacid used to ease heartburn, calcium acetate (PhosLo), a treatment for chronic kidney disease, and calcium gluconate, a medication that’s mainly given in hospitals as an infusion into a vein (intravenous or “IV”) for certain medical emergencies (Chakraborty, 2021). 

Calcium gluconate can also be an ingredient in dietary supplements that you can buy over the counter and take by mouth. However, other calcium salts like calcium carbonate (Caltrate, Tums) and calcium citrate (Citracal) are far more common because they are much easier for your body to absorb than oral calcium gluconate (Saljoughian, 2015). 

Calcium gluconate is approved by the Food and Drug Administration (FDA) for the short-term treatment of sudden, very low calcium levels (acute symptomatic hypocalcemia). This sudden drop in calcium may cause severe symptoms, such as muscle twitching or spasms, seizures, tetany, or changes to the heart’s normal rhythm (Cooper, 2008). 

Common causes of acute symptomatic hypocalcemia include kidney disease, lack of parathyroid hormone, or vitamin D deficiency. Administering calcium directly into the blood can quickly correct the low level (Cooper, 2008).

Calcium gluconate can also be used off-label to treat other medical emergencies or conditions. Off-label uses for calcium gluconate include the treatment of (Vanden Hoek, 2010; Chakraborty, 2021):

• Cardiac arrest (heart attack) or arrhythmia due to high potassium or magnesium levels

• Overdose of heart medications called beta-blocker or calcium-channel blockers

• Hypermagnesemia (too-high blood levels of magnesium)

• Chemical burns caused by an acid called hydrofluoric acid that’s used to manufacture refrigerants and fluorescent light bulbs, among other things (CDC, 2018)

It may not seem logical to you that doctors give calcium gluconate for these problems when several of them involve other things like potassium or magnesium. While calcium gluconate does not affect or correct these imbalances, it helps to protect heart muscle cells and support heart function and rhythm. So, in these situations, doctors will use other treatments in addition to calcium gluconate (Hollander-Rodriguez, 2006).

Common side effects of the intravenous form of calcium gluconate include (Fresenius-Kabi, 2021; Chakraborty, 2021):

• Hypotension (decreased blood pressure)

• Flushing

• Dizziness

• Fainting

• Bradycardia (slowed heart rate)

Less frequently, calcium gluconate can cause severe irritation or damage to the skin and soft tissue. Healthcare professionals call this extravasation. It occurs if calcium gluconate leaks out of your vein and penetrates the area around the injection site. 

Treatment with calcium gluconate runs a risk of raising calcium levels too much, which can lead to heart problems. Since the drug is typically given in a hospital or other healthcare setting, doctors and nurses will look out for these risks and, if necessary, use an electrocardiogram (ECG) to monitor your heart.

Calcium gluconate is not a popular ingredient in oral dietary supplements. But when it is used, it can cause side effects similar to other oral calcium supplements, such as gas, bloating, and constipation (NIH, 2021).

Calcium gluconate dosage depends on how it's administered: intravenously or orally.

Intravenous infusions

The intravenous form of calcium gluconate comes in a solution. It contains 20 mg of calcium gluconate per milliliter (mL) and is typically administered in a hospital by a healthcare professional (Fresenius-Kabi, 2021).

If you’re being treated for hypocalcemia (low calcium), a healthcare provider will check your blood calcium levels after the infusion. If your calcium is still low, you might get another infusion until your calcium levels are back to normal. If you’re being treated for a heart problem, the healthcare provider will determine the appropriate calcium gluconate dose for you. 

Older people (65+) and those with kidney problems usually get lower doses of calcium gluconate.

Oral calcium supplements

The oral form of calcium gluconate is available as an ingredient in over-the-counter (OTC) dietary supplements. If you take one of these OTC supplements, it’s important to follow their dosing instructions. According to the National Institutes of Health, the recommended dietary allowance (RDA) for calcium for adults is 1,000 mg per day. The RDA is the amount a healthy individual should consume (from foods or supplements) each day to meet their body’s nutritional needs (NIH, 2021). 

Calcium gluconate may interact with certain medications. Examples of medications that may interact with calcium gluconate include (Fresenius-Kabi, 2021):

• Digoxin, a heart medication

• Calcium channel blockers, a blood pressure and heart medication

• Tetracycline antibiotics, such as minocycline, used to treat infections

• In newborns, calcium gluconate can interact with a popular antibiotic (ceftriaxone) and lead to life-threatening organ damage. 

• Vitamins or drugs that can affect calcium levels, such as: vitamin D; vitamin A; thiazide diuretics like hydrochlorothiazide, which is used to treat excess fluid retention or high blood pressure; estrogen-like ingredients used in birth control and other hormone-related medications; calcipotriene, a form of vitamin D that’s used as a topical treatment for psoriasis, a skin condition

If you have questions about calcium gluconate or other forms of calcium, ask a pharmacist or healthcare provider.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

December 08, 2021

Written by

Patricia Weiser, PharmD

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.