Magnesium Chloride works by replenishing magnesium levels in your body, where it serves as a cofactor for over 300 enzymatic reactions that keep your nerves, muscles, heart, and bones functioning properly.

What Magnesium Chloride Does in Your Body

When you take Magnesium Chloride — whether as an oral tablet or an IV injection — it breaks down and releases magnesium ions (Mg²⁺) into your bloodstream. These magnesium ions then go to work throughout your body in several critical ways:

Nerve and Muscle Function

Magnesium is essential for proper nerve signaling and muscle contraction. It acts as a natural calcium channel blocker — meaning it helps regulate how much calcium enters your nerve and muscle cells. Too much calcium flowing into these cells can cause overstimulation, which leads to muscle cramps, spasms, and twitching. Magnesium keeps this in balance.

This is why people with low magnesium often experience muscle cramps, restless legs, and eye twitching. Restoring magnesium levels with Magnesium Chloride can relieve these symptoms.

Heart Rhythm

Your heart is a muscle, and it depends heavily on the right balance of electrolytes — including magnesium — to beat regularly. Magnesium helps stabilize the electrical signals that control your heartbeat. When magnesium levels drop, you're more likely to experience arrhythmias (irregular heartbeat). In emergency settings, IV Magnesium Chloride is sometimes used to treat dangerous arrhythmias like torsades de pointes.

Energy Production

Magnesium is required for your body to produce ATP — the molecule that powers nearly every process in your cells. Without enough magnesium, your cells can't produce energy efficiently, which is why fatigue is one of the hallmark symptoms of magnesium deficiency.

Bone Health

About 60% of the magnesium in your body is stored in your bones. Magnesium helps with bone mineralization — the process of strengthening bone tissue. Low magnesium levels have been linked to lower bone density and higher fracture risk.

The Sodium-Potassium Pump

Magnesium is required for the proper functioning of the sodium-potassium ATPase pump — a protein found in every cell in your body. This pump is responsible for maintaining the right balance of sodium and potassium inside and outside your cells, which is essential for nerve impulses, muscle contractions, and fluid balance.

How Long Does It Take to Work?

The timeline depends on the form and the severity of your deficiency:

• IV Magnesium Chloride: Effects begin within minutes. This is why the injectable form is used in emergency settings for severe deficiency, cardiac arrhythmias, and eclampsia.
• Oral tablets: You may begin to notice improvements in symptoms like muscle cramps and sleep quality within a few days to a week. However, fully replenishing your body's magnesium stores can take several weeks of consistent supplementation.
• Blood level changes: Serum magnesium levels typically begin to improve within 24 to 48 hours of starting oral supplementation, but tissue-level magnesium (stored in bones and muscles) takes longer to normalize.

Your doctor may recheck your magnesium levels after 2 to 4 weeks to see how you're responding. For details on dosing, see our Magnesium Chloride uses and dosage guide.

How Long Does It Last?

Magnesium Chloride doesn't have a sharp "on/off" like some medications. Here's what to know:

• Daily supplementation maintains levels. Oral Magnesium Chloride is typically taken daily to maintain adequate magnesium levels. If you stop taking it, your levels will gradually decline — especially if the underlying cause of your deficiency (like poor diet or a medication that depletes magnesium) hasn't been addressed.
• IV doses provide a short-term boost. A single IV dose raises magnesium levels quickly but the effects don't last indefinitely. The body continues to excrete magnesium through the kidneys, so ongoing supplementation or repeat IV doses may be needed.

What Makes Magnesium Chloride Different from Other Forms?

Not all magnesium supplements are the same. Here's how Magnesium Chloride compares:

Magnesium Chloride stands out for its balance of good absorption and relatively mild side effects. The delayed-release formulation (Slow-Mag) further reduces stomach irritation, making it one of the best-tolerated options for daily use.

If you're considering switching forms, check out our guide on alternatives to Magnesium Chloride.

Final Thoughts

Magnesium Chloride works by delivering magnesium ions to your body, where they support hundreds of essential processes — from keeping your heart beating regularly to helping your muscles relax and your cells produce energy. It's well-absorbed, effective, and available in forms that suit different needs.

Whether you're taking Magnesium Chloride for a diagnosed deficiency or to manage symptoms like muscle cramps, understanding how it works can help you stick with your treatment plan and know what to expect.

Need to find Magnesium Chloride? Search Medfinder to check pharmacy availability near you.