What does high magnesium in water do?

November 27, 2025 •

6 min read

Hard water, defined by its high mineral content, is found in many places and contains significant amounts of magnesium. This naturally occurring mineral in water can provide important health benefits, but very high concentrations can also lead to adverse effects. Understanding what high magnesium in water does is key for both your health and home maintenance.

Quick Summary

High magnesium levels in water, characteristic of hard water, provide essential minerals for health but can have downsides. It may offer cardiovascular benefits but also cause digestive issues like diarrhea and create household problems like scale buildup on pipes and appliances. The taste of water can also be altered by high magnesium content.

Key Points

Cardiovascular Health: Moderately high magnesium in drinking water has been linked to a reduced risk of cardiovascular diseases, including acute myocardial infarction.
Digestive Effects: High concentrations of magnesium salts, especially sulfate, can cause a laxative effect leading to diarrhea and stomach cramps.
Home Appliance Damage: As a component of hard water, high magnesium levels result in limescale buildup on pipes, faucets, and inside water-using appliances, reducing their efficiency.
Cleaning Inefficiency: Hard water prevents soap and detergents from lathering effectively, leading to soap scum and requiring more product for cleaning.
Flavor Profile: Water high in magnesium may have a noticeable bitter or metallic taste.
Risk for Kidney Patients: Individuals with impaired kidney function are more susceptible to hypermagnesemia from excessive magnesium intake, as their bodies cannot properly excrete it.
Treatment Solutions: Water softeners can remove high levels of magnesium, resolving household issues caused by hard water, while water conditioners prevent scale formation.

The Effects of High Magnesium in Drinking Water on Your Body

Magnesium is a vital mineral that supports over 300 biochemical reactions in the human body, including nerve function, muscle activity, and protein synthesis. The concentration of magnesium in your drinking water can significantly impact your overall health, offering both advantages and potential disadvantages depending on the levels.

Health Benefits of Moderately High Magnesium Water

Drinking water with moderate to high levels of magnesium can be beneficial, particularly for those with a low dietary intake of the mineral. Magnesium is essential for proper bone health, as it works with calcium and vitamin D to regulate bone tissue formation. A sufficient intake of waterborne magnesium has also been linked to cardiovascular health benefits. Studies show an inverse relationship between magnesium levels in drinking water and mortality from cardiovascular diseases and acute myocardial infarction in some populations. It is believed to have anti-stress actions that help protect against coronary heart disease. Furthermore, adequate magnesium levels can help regulate blood pressure by relaxing blood vessels and controlling the heart's electrical signaling. For individuals with type 2 diabetes, magnesium is crucial for insulin regulation, and the extra intake from hard water can be beneficial.

Potential Side Effects of Excessively High Magnesium Water

While beneficial at moderate levels, a very high concentration of magnesium in water can pose problems. The most common side effect is a laxative effect. This is particularly true for magnesium sulfate, a compound with osmotic properties that draws water into the intestines, leading to diarrhea, stomach cramps, and potentially dehydration. Most healthy individuals excrete excess magnesium via the kidneys, but those with kidney dysfunction are at a much higher risk of developing hypermagnesemia, a rare but serious condition of excessively high blood magnesium.

How High Magnesium Water Affects Your Home

Beyond internal health, high magnesium levels also have noticeable effects on your home's plumbing, appliances, and daily cleaning tasks. This phenomenon is commonly known as "hard water." The effects include:

Limescale buildup: A hard, chalky residue can form inside pipes, on faucets, and on the heating elements of appliances like kettles and water heaters, reducing their efficiency and lifespan.
Ineffective cleaning: Soap and detergents react with hard water minerals to form a residue called "soap scum," which prevents them from lathering properly. This means you need to use more product for laundry, dishes, and personal hygiene.
Cloudy dishes: Hard water often leaves cloudy spots and streaks on glassware and other dishes after washing, which are mineral deposits left behind as the water evaporates.
Skin and hair issues: The mineral residue can strip natural oils from the skin and hair, leading to dryness, irritation, and dull, brittle hair. People with sensitive skin or conditions like eczema may experience worsened symptoms.

High Magnesium Water: Health and Household Comparison


Feature	Health Effects (Drinking)	Household Effects (Using)
Benefits	Contributes to daily magnesium intake; Supports cardiovascular health; Aids bone health and metabolism.	Can enhance the taste of certain beverages, like coffee.
Drawbacks	Can cause a laxative effect, leading to diarrhea; May lead to unpleasant bitter or metallic taste; Poses risk for individuals with kidney issues.	Leaves mineral scale buildup on pipes and appliances; Reduces the effectiveness of soaps and detergents; Can cause dry skin and hair; Leaves spots on dishes.

Solutions for High Magnesium Water

For those who experience the adverse effects of high magnesium water, several treatment options are available. The most common method is a water softener, which uses an ion exchange process to replace magnesium and calcium ions with sodium or potassium ions. Water conditioners are an alternative that alters the mineral structure to prevent scale buildup without removing the minerals. The specific best solution depends on whether you want to remove the minerals for appliance protection or simply manage their effects. For more information on water quality, the U.S. Geological Survey provides helpful resources on water hardness.

Conclusion

In summary, what high magnesium in water does is create a dichotomy of effects. On one hand, it can be a valuable source of a crucial dietary mineral, potentially contributing to better cardiovascular health and bone density. On the other hand, excessively high concentrations can lead to unwanted digestive issues and significant household problems, including scale buildup and ineffective cleaning. Most healthy individuals can tolerate moderately high magnesium levels from drinking water, as the body effectively regulates and excretes the excess. However, for those with pre-existing conditions or who are bothered by the household inconveniences, proper testing and treatment, such as a water softener, can mitigate the negative impacts.

Learn more about water hardness from the USGS

Note: The World Health Organization has no official maximum guideline for magnesium in drinking water, though some national standards exist.

What Does High Magnesium in Water Do: Key Takeaways

Health Benefits: High magnesium water is a natural source of this essential mineral, supporting bone and heart health, and potentially reducing risks of certain diseases.
Adverse Health Effects: Excessive intake, particularly from supplements or very high water concentrations, can lead to a laxative effect and gastrointestinal distress.
Taste Profile: Depending on its mineral composition, high magnesium can impart a bitter or metallic taste to water.
Household Impact: High magnesium is a key component of hard water, causing limescale buildup in pipes and appliances, reducing their efficiency and lifespan.
Cleaning Efficiency: Hard water reduces the lathering ability of soaps and detergents, leading to lower cleaning effectiveness and the formation of soap scum.
Skin and Hair Effects: The minerals in hard water can affect the skin and hair, potentially causing dryness and irritation.
Treatment Options: Water softeners use ion exchange to remove excess magnesium, while water conditioners alter the mineral structure to prevent buildup.

FAQs About High Magnesium in Water

Question: Is hard water a health risk? Answer: Hard water, which is high in calcium and magnesium, is not generally considered a health risk for most people and can even contribute positively to overall mineral intake. However, excessively high levels may cause digestive issues in sensitive individuals.

Question: Can high magnesium water cause diarrhea? Answer: Yes, very high concentrations of magnesium salts, especially magnesium sulfate, can have a laxative effect and cause diarrhea, stomach cramps, and nausea. This is more likely with certain types of mineral water or supplements rather than typical tap water.

Question: How does high magnesium water affect my home appliances? Answer: High magnesium water, or hard water, causes limescale buildup inside appliances that use water, such as kettles, water heaters, and dishwashers. This buildup reduces efficiency, increases energy consumption, and can shorten the appliance's lifespan.

Question: Why does my water taste bitter or metallic? Answer: A bitter or metallic taste in your water can be a sign of high mineral content, including magnesium. The specific taste can vary based on the combination of minerals present.

Question: Can I get too much magnesium from drinking water? Answer: For most healthy individuals with normal kidney function, it is difficult to get a magnesium overdose solely from drinking water, as the body effectively excretes excess amounts. The risk is higher for those with kidney disease or those who also take magnesium supplements.

Question: How can I know the magnesium level in my water? Answer: You can contact your local water utility or health department to inquire about a water quality report, or you can purchase a test kit for your well water. Water hardness is typically measured in milligrams per liter (mg/L).

Question: How can I treat high magnesium levels in my water? Answer: Water softeners are the most effective method for treating hard water by replacing magnesium and calcium with sodium. Alternatively, water conditioners can prevent scale buildup without removing the minerals. For digestive issues related to high magnesium, it is best to consult a healthcare provider.

Frequently Asked Questions

Hard water, which contains minerals like magnesium and calcium, is generally considered safe and can contribute to your daily mineral intake. Some studies even suggest protective health benefits, such as a lower risk of certain cardiovascular diseases.

Yes, particularly when magnesium is present as a sulfate, high concentrations can cause a laxative effect. This is more commonly associated with certain mineral waters or supplements rather than typical tap water, but can cause diarrhea, stomach cramps, and nausea.

High magnesium water, a characteristic of hard water, can negatively affect skin and hair. The minerals can leave a residue that strips natural oils, causing dryness and irritation, and can make hair feel brittle and dull.

High magnesium levels lead to the formation of limescale, a hard, chalky deposit that clogs pipes and coats the heating elements of appliances like dishwashers and water heaters. This reduces their efficiency and can cause damage over time.

A bitter or metallic taste in water can be attributed to a high concentration of minerals, including magnesium. The taste profile can be complex and depends on the specific combination of dissolved salts.

While healthy individuals can typically excrete excess magnesium, those with pre-existing kidney disease are at a higher risk of developing hypermagnesemia, a serious condition caused by an overabundance of magnesium in the blood.

A water softener actively removes magnesium and calcium ions through an ion exchange process, effectively reducing water hardness. A water conditioner, on the other hand, alters the mineral structure to prevent scale buildup without removing the minerals themselves.