What You Should Know About Magnesium Chloride Side Effects

Magnesium Chloride is one of the most widely used forms of magnesium supplementation. Whether you're taking oral tablets like Slow-Mag for a deficiency or receiving IV Magnesium Chloride in a hospital, it's generally well tolerated. But like any medication or supplement, it can cause side effects — some mild, some serious.

This guide covers what to expect, which side effects are normal, and when you should call your doctor.

What Is Magnesium Chloride?

Magnesium Chloride is a mineral supplement used to treat and prevent low magnesium levels (hypomagnesemia). It comes in oral tablets, capsules, liquids, and injectable solutions. For a deeper look at how it works and what it's used for, see our guides on what Magnesium Chloride is and how it works in your body.

Common Side Effects

Most people who take Magnesium Chloride at recommended doses experience few or no side effects. When they do occur, the most common ones are digestive:

• Diarrhea — This is the most frequently reported side effect. Magnesium draws water into the intestines, which can loosen stools. This is more likely at higher doses.
• Nausea — Some people feel mildly nauseous, especially when taking Magnesium Chloride on an empty stomach.
• Stomach cramps or upset — Abdominal discomfort can occur, particularly with immediate-release formulations.
• Bloating and gas — These are usually mild and temporary.

These side effects are usually dose-related. If you're experiencing digestive issues, taking your dose with food and a full glass of water often helps. Delayed-release tablets like Slow-Mag are specifically designed to reduce stomach irritation.

Serious Side Effects

Serious side effects from oral Magnesium Chloride are rare when taken at recommended doses. However, they can happen — particularly with high doses, IV administration, or in people with kidney problems. Watch for these warning signs:

• Severe hypotension (dangerously low blood pressure) — Symptoms include dizziness, fainting, or feeling lightheaded when standing up.
• Respiratory depression — Slow or shallow breathing is a sign of magnesium toxicity and requires immediate medical attention.
• Irregular heartbeat or cardiac changes — Magnesium affects heart rhythm. Too much can cause dangerous arrhythmias. If you feel your heart racing, skipping beats, or pounding unusually, call your doctor.
• Loss of deep tendon reflexes — This is an early sign of hypermagnesemia (too much magnesium in the blood) and is more common with IV administration.
• Extreme drowsiness or muscle weakness — If you feel unusually weak or can barely stay awake, seek medical attention.

When to call your doctor immediately: If you experience difficulty breathing, chest pain, severe dizziness, confusion, or muscle weakness that makes it hard to move, call your doctor or go to the emergency room right away.

Who Is Most at Risk for Side Effects?

Certain groups need to be especially careful with Magnesium Chloride:

People with Kidney Disease

Your kidneys are responsible for filtering excess magnesium from your blood. If your kidneys aren't working well (GFR below 30 mL/min), magnesium can build up to dangerous levels. People with severe kidney disease should generally avoid Magnesium Chloride or use it only under close medical supervision with regular blood monitoring.

Older Adults

Kidney function naturally declines with age. Older adults may need lower doses and more frequent monitoring of magnesium levels.

Pregnant and Breastfeeding Women

Magnesium Chloride should be used during pregnancy only under a doctor's guidance. While magnesium is important during pregnancy, the dose must be carefully managed. IV magnesium is sometimes used for pre-eclampsia, but this is done in a hospital setting with constant monitoring.

People Taking Certain Medications

If you're on medications that interact with magnesium — like digoxin, certain antibiotics, or neuromuscular blocking agents — your risk of side effects may be higher. Read our full guide on Magnesium Chloride drug interactions to learn more.

How to Manage Side Effects

Here are practical steps to reduce or manage Magnesium Chloride side effects:

1. Take it with food. This is the simplest way to reduce nausea and stomach upset. A full glass of water also helps.
2. Use delayed-release tablets. Products like Slow-Mag are designed to dissolve slowly in your digestive tract, which reduces irritation.
3. Split your dose. Instead of taking all your magnesium at once, divide it into two or three smaller doses throughout the day. This improves absorption and reduces digestive side effects.
4. Lower the dose. If diarrhea is persistent, talk to your doctor about reducing your dose. Sometimes a small reduction makes a big difference.
5. Stay hydrated. Since magnesium can cause diarrhea, make sure you're drinking enough water to prevent dehydration.
6. Monitor your levels. Regular blood tests can help your doctor ensure your magnesium levels are in the safe range — not too low, not too high.

If you're having trouble tolerating Magnesium Chloride, your doctor might suggest trying a different form of magnesium, like magnesium glycinate or magnesium citrate, which may be easier on your stomach.

Final Thoughts

For most people, Magnesium Chloride is safe and causes only mild digestive side effects — if any. The key is to take it at the right dose, with food, and to work with your doctor if you have kidney problems or take medications that could interact with magnesium.

Serious side effects like breathing problems, extreme weakness, or heart rhythm changes are rare but need immediate medical attention. Don't ignore these symptoms.

If you're looking for Magnesium Chloride or need help finding it in stock, check Medfinder for real-time pharmacy availability near you.