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Generic name: calcium carbonate and magnesium chlorideKAL-see-um-KAR-boe-nate-and-mag-NEE-see-um-KLOR-ide ]
Brand names: Mag64, MagDelay, Magnesium Chloride With Calcium, Nu-Mag, Slow Magnesium Chloride with Calcium, Slow-Mag, SlowMag Muscle + Heart
Drug class: Minerals and electrolytes

Medically reviewed by on Aug 16, 2023. Written by Cerner Multum.

What is MagDelay?

Calcium and magnesium are naturally occurring minerals. Calcium is needed for bone formation and maintenance. Magnesium helps maintain muscle function and normal heart rhythm.

MagDelay is a combination medicine used as a supplement. MagDelay is given when your diet does not provide enough of these minerals, or when they are lost through perspiration.

MagDelay may also be used for purposes not listed in this medication guide.

MagDelay side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

MagDelay may cause serious side effects. Stop using MagDelay and call your doctor at once if you have:

Common side effects of MagDelay may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

You should not use MagDelay if you have ever had an allergic reaction to an antacid or vitamin/mineral supplement that contains calcium carbonate or magnesium chloride.

Ask a doctor or pharmacist if this medicine is safe to use if you have:

Ask a doctor before using this medicine if you are pregnant or breastfeeding. Your dose needs may be different during pregnancy or while you are nursing.

How should I take MagDelay?

Use exactly as directed on the label, or as prescribed by your doctor.

Swallow the tablet whole and do not crush, chew, or break it.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Since MagDelay is used when needed, you may not be on a dosing schedule. Skip any missed dose if it's almost time for your next dose. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking MagDelay?

Avoid taking other medicines at the same time you take MagDelay.

What other drugs will affect MagDelay?

Calcium carbonate can make it harder for your body to absorb certain drugs, making them less effective. If you take other medicines, take your MagDelay dose 2 hours before or 2 hours after you take the other medicine.

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may affect MagDelay, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

More about MagDelay (calcium carbonate / magnesium chloride)

Patient resources

Other brands

Slow-Mag, Mag 64, Nu-Mag

Related treatment guides

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.