Yes, Magnesium Reacts with Carbonated Water (But There's a Catch)

January 3, 2026 •

4 min read

Interestingly, a simple kitchen chemistry experiment reveals that a form of magnesium readily reacts with carbonated water to create a highly bioavailable compound. The question 'Does magnesium react with carbonated water?' is more nuanced than it appears, as the type of magnesium used fundamentally changes the outcome and safety of the reaction.

Quick Summary

The reaction between magnesium and carbonated water hinges on the magnesium's form. While elemental magnesium reacts minimally, magnesium hydroxide combines with carbonic acid to form magnesium bicarbonate, a soluble and easily absorbed mineral supplement.

Key Points

Elemental vs. Compound: The reaction depends on the type of magnesium; pure elemental magnesium reacts minimally with carbonated water at room temperature.
Magnesium Hydroxide Reaction: Magnesium hydroxide (Milk of Magnesia) readily reacts with the carbonic acid in carbonated water, forming magnesium bicarbonate.
Bioavailable Product: The end product of the magnesium hydroxide reaction, magnesium bicarbonate, is a highly soluble and easily absorbed form of magnesium.
DIY Supplement: This chemical reaction is the basis for creating a cost-effective, homemade magnesium supplement known as magnesium bicarbonate water.
Gentle on Digestion: Magnesium bicarbonate is absorbed more efficiently than other forms like magnesium oxide, making it gentler on the digestive system and less likely to cause laxative effects.
Visible Change: The reaction between magnesium hydroxide and carbonated water is visible, as a cloudy mixture transforms into a clear solution over time.

The Core Chemical Differences: Elemental vs. Compounds

To understand how magnesium reacts with carbonated water, it is crucial to distinguish between elemental magnesium (the pure metal) and magnesium compounds, such as magnesium hydroxide (Milk of Magnesia).

Elemental Magnesium Metal and Carbonated Water

At room temperature, elemental magnesium metal, which is a reactive alkaline earth metal, has a protective oxide layer that prevents it from having a visible, rapid reaction with water, including carbonated water. The slow reaction produces magnesium hydroxide and hydrogen gas, but the resulting magnesium hydroxide layer insulates the rest of the metal from further contact with water, effectively stopping the process. However, the presence of carbonic acid (produced when CO₂ dissolves in water) slightly accelerates the reaction, but it is not a dramatic or immediate change.

Magnesium Hydroxide and Carbonated Water

The most notable and practical reaction occurs when a magnesium compound, specifically magnesium hydroxide, is mixed with carbonated water. This is the basis for many homemade and commercially available magnesium bicarbonate supplements. The reaction is straightforward and involves an acid-base neutralization:

$Mg(OH)_2(s) + 2CO_2(aq) \to Mg(HCO_3)_2(aq)$

In this equation, magnesium hydroxide, a sparingly soluble base, reacts with the carbonic acid ($H_2CO_3$), which is formed by the dissolved carbon dioxide ($CO_2$) in the water. The products are water and magnesium bicarbonate ($Mg(HCO_3)_2$), a compound that exists only in aqueous solution and is highly soluble. The reaction is visually apparent as the cloudy, white magnesium hydroxide suspension becomes a clear solution as the magnesium bicarbonate is formed.

Comparison of Magnesium Reactivity with Carbonated Water


Feature	Elemental Magnesium Metal (Mg)	Magnesium Hydroxide (Mg(OH)₂)
Starting Material	Solid, pure metal, often as flakes or strips.	White powder or liquid suspension (Milk of Magnesia).
Reacts with Carbonated Water?	Minimally and very slowly due to a passivating oxide layer.	Yes, a purposeful and well-known reaction.
End Product	Magnesium hydroxide and hydrogen gas, but reaction is stifled.	Magnesium bicarbonate ($Mg(HCO_3)_2$), a soluble salt.
Reaction Speed	Extremely slow at room temperature.	Quick, resulting in a clear solution within minutes to hours.
Safety & Practicality	Not practical for creating a supplement; can be highly reactive when heated (e.g., in fire).	Safe for preparing supplements when done correctly, resulting in a gentle, bioavailable form.
Visible Signs of Reaction	Few, small bubbles forming very slowly over a long period.	Initial fizzing and bubbling, followed by the solution clearing as the solid dissolves.

Practical Applications: Creating a Bioavailable Supplement

Creating your own magnesium bicarbonate water is a known method for increasing magnesium intake in a highly absorbable form. The process involves mixing magnesium hydroxide powder with unflavored carbonated water. The resulting solution is often stored in a sealed bottle to maintain its stability, as magnesium bicarbonate will slowly decompose back into insoluble magnesium carbonate and carbon dioxide if exposed to air.

Steps for a DIY Magnesium Bicarbonate Solution:

Gather Ingredients: Obtain food-grade magnesium hydroxide powder and plain, unflavored carbonated water.
Prepare the Container: Use a clean, sealed glass bottle. Pour out a small amount of the carbonated water to create headspace for the reaction.
Combine: Add a measured amount of magnesium hydroxide powder to the bottle. A common ratio is 1 teaspoon of powder per liter of water.
Shake and Dissolve: Seal the bottle quickly and shake vigorously for 1-2 minutes. The mixture will turn cloudy as the powder suspends.
Wait and Store: Place the bottle in the refrigerator. The solution will gradually become clear over several hours as the reaction completes and the magnesium bicarbonate dissolves completely.

The Bioavailability Advantage

One of the main reasons for creating magnesium bicarbonate water is its superior bioavailability. Many common magnesium supplements, like magnesium oxide, have low absorption rates. The liquid magnesium bicarbonate bypasses this issue and is absorbed efficiently, making it gentle on the stomach and effective for supplementation. This makes it a popular option for those seeking to boost their magnesium levels without the common laxative side effects associated with other forms.

Conclusion: The Chemistry is Context-Dependent

The question of whether magnesium reacts with carbonated water is answered by specifying the form of magnesium. Elemental metal magnesium has only a negligible reaction due to its protective oxide layer. In contrast, the intentional mixing of magnesium hydroxide with carbonated water, which contains carbonic acid, results in a well-understood chemical reaction. This process produces magnesium bicarbonate, a highly absorbable and stomach-friendly form of magnesium that is popular for supplementation. Understanding this distinction is key for anyone interested in the chemistry or practical application of these compounds.

For additional scientific context on magnesium and its bioavailability from different sources, see this related study: Predicting and Testing Bioavailability of Magnesium Supplements.

Frequently Asked Questions

When magnesium hydroxide is added to carbonated water, it reacts with the carbonic acid to form a clear solution of magnesium bicarbonate. This is an acid-base neutralization reaction.

It is safe to mix magnesium hydroxide powder, often used for supplementation, with carbonated water. The reaction is controlled and intentionally performed to create magnesium bicarbonate. However, mixing elemental magnesium metal is not a safe or practical way to create a supplement.

The mixture becomes clear because the insoluble magnesium hydroxide powder reacts to form soluble magnesium bicarbonate. As the solid powder dissolves into the new compound, the solution loses its cloudiness.

If you mix magnesium hydroxide with regular tap water, it will not dissolve completely. Tap water lacks the dissolved carbon dioxide (and thus the carbonic acid) needed to convert the insoluble magnesium hydroxide into soluble magnesium bicarbonate.

Yes, the reaction consumes the dissolved carbon dioxide from the water to create the bicarbonate compound. This can cause the water to lose some or all of its fizziness.

Magnesium bicarbonate is highly soluble in water, which allows for better absorption in the digestive tract compared to poorly absorbed forms like magnesium oxide or magnesium carbonate. This higher absorption leads to better bioavailability.

No, this specific reaction relies on magnesium hydroxide. Other forms, like magnesium citrate or glycinate, will likely not react in the same way or produce the same product. Always follow supplement instructions.