What Are the Disadvantages of Magnesium in Drinking Water?

November 12, 2025 •

4 min read

While the body requires magnesium for essential functions, the World Health Organization notes that very hard water can provide an important supplementary intake, but it can also have undesirable side effects when present in excess. These disadvantages of magnesium in drinking water affect both your health and household infrastructure.

Quick Summary

High magnesium levels in drinking water can lead to digestive discomfort, interfere with appliance performance, and may pose a health risk for individuals with impaired kidney function.

Key Points

Digestive Discomfort: High levels of magnesium, especially from salts like sulfate, can cause a laxative effect leading to diarrhea, nausea, and abdominal cramps.
Risk for Kidney Patients: Individuals with impaired kidney function are at a high risk for hypermagnesemia (magnesium overdose) from excessive intake, which can cause serious health complications.
Household Limescale Buildup: Magnesium is a primary component of hard water, which causes limescale to accumulate in pipes and appliances, reducing efficiency and lifespan.
Poor Water Quality and Taste: Elevated magnesium can impart a bitter or metallic taste to drinking water and cause a cloudy appearance.
Soap Ineffectiveness: Hard water prevents soap from lathering correctly, leading to reduced cleaning efficacy, soap scum buildup, and potential skin irritation.
Potential for Appliance Damage: Mineral deposits from hard water can damage and shorten the lifespan of household appliances like water heaters, dishwashers, and washing machines.

Health Risks Associated with High Magnesium Intake

For most healthy individuals, the kidneys effectively excrete excess magnesium, making toxicity from drinking water alone rare. However, certain populations and conditions can make high magnesium levels a concern. It is most often associated with high doses from supplements or medication, but high concentrations in water can contribute to these issues.

Digestive Issues

One of the most immediate and common side effects of high magnesium, particularly in the form of magnesium sulfate (Epsom salt) or magnesium chloride, is its laxative effect. This is because these salts pull water into the intestines, softening stool and increasing bowel motility. While sometimes used intentionally to relieve constipation, chronically consuming high-magnesium water can lead to uncomfortable and persistent symptoms, such as:

Diarrhea
Nausea
Abdominal cramping
Stomach pain

Individuals with pre-existing gastrointestinal conditions like irritable bowel syndrome may be more sensitive to these effects.

Risks for Individuals with Kidney Disease

For those with chronic kidney disease or impaired renal function, the body's ability to excrete excess magnesium is diminished. This can lead to a dangerous buildup of the mineral in the blood, a condition called hypermagnesemia. Symptoms of severe hypermagnesemia can be serious and include:

Muscle weakness
Low blood pressure (hypotension)
Drowsiness and confusion
Difficulty breathing
Abnormal heart rhythm
In very severe cases, cardiac arrest

For this reason, people with kidney conditions are often advised to monitor their magnesium intake carefully, including from drinking water.

Interference with Medication Absorption

Magnesium can interfere with the absorption of certain medications, including some antibiotics (like tetracycline) and bisphosphonates (for osteoporosis). If drinking water is the source of high magnesium, it could potentially reduce the effectiveness of these treatments, although supplementation is the more common cause of such interactions.

Household and Aesthetic Drawbacks of Hard Water

High concentrations of magnesium (and calcium) are the primary cause of hard water. This not only affects the water's taste and how it interacts with soap but also causes significant damage to plumbing and appliances over time.

Limescale and Appliance Damage

When hard water is heated, magnesium and calcium carbonates precipitate out of the solution and form a hard, crusty deposit known as limescale. This can occur in:

Pipes and faucets, reducing water pressure.
Water heaters, decreasing energy efficiency and leading to premature failure.
Dishwashers and washing machines, leaving white streaks and reducing cleaning effectiveness.

Poor Taste and Aesthetic Issues

High magnesium can give water a distinct, and often unpleasant, bitter or metallic taste. It can also cause water to appear cloudy, which, while not a health risk, can be unappealing to consumers. The mineral deposits also lead to unsightly stains on sinks, bathtubs, and clothing.

Soap Inefficiency and Skin Problems

Hard water prevents soap from lathering effectively, leading to wastage. Instead of a rich lather, it forms a sticky scum with soap. This can also lead to issues with personal hygiene, leaving a film on skin and hair. For individuals with sensitive skin, including those with conditions like atopic dermatitis (eczema), some studies suggest a link between exposure to hard water and aggravated symptoms, though results are not conclusive.

High vs. Low Magnesium in Drinking Water: A Comparison


Feature	High Magnesium in Water	Low Magnesium in Water
Health Effects	Can cause digestive upset like diarrhea in some individuals; risk of hypermagnesemia in those with kidney issues; potential medication interference.	Possible association with increased risk of certain cardiovascular diseases in some regions, though evidence is inconsistent and correlation is not causation.
Aesthetic Effects	May have a bitter or metallic taste; can appear cloudy or have a white, chalky residue.	Typically has a clean, neutral taste and appearance, preferred by many consumers.
Household Effects	Limescale buildup in pipes and appliances, leading to reduced efficiency, damage, and clogged plumbing.	Less risk of limescale buildup; better for appliances and plumbing infrastructure.
Soap Interaction	Reacts with soap to form soap scum, reducing lather and wasting product; can leave residue on skin and clothes.	Lathers easily with soap and detergents, leading to more efficient cleaning of laundry, dishes, and bodies.

Conclusion

While some magnesium in drinking water is beneficial, excessive amounts, especially when combined with high calcium levels to form hard water, present distinct disadvantages. For the average, healthy person, the digestive and taste issues are the most likely and noticeable problems. For individuals with underlying health conditions, particularly impaired kidney function, consistently high levels of magnesium from water or other sources can pose more serious health risks. In the home, the damage and inefficiency caused by limescale buildup is a significant long-term concern. Understanding these disadvantages is key to making informed decisions about water treatment. Methods such as water softening can help mitigate the issues caused by hard water.

How to Reduce Excess Magnesium

For those affected by the disadvantages of magnesium in drinking water, several solutions exist to reduce its concentration:

Water Softening Systems: The most effective method for a whole-house solution involves an ion exchange system, which replaces magnesium and calcium ions with sodium or potassium ions.
Reverse Osmosis (RO) Filtration: RO systems can effectively demineralize water, but some variations can remineralize it to a desired level.
Specialty Filters: Ion-exchange resin pitchers or faucet filters can reduce hardness for drinking and cooking water.

It is important to test your water first to understand the exact mineral composition and consult with a professional to choose the right treatment method for your needs. Always consult a healthcare provider if you have health concerns related to your water intake.

Frequently Asked Questions

Yes, high levels of magnesium salts, such as magnesium sulfate and chloride, are known to have a laxative effect, which can lead to diarrhea, nausea, and stomach cramps.

Yes, for individuals with poor kidney function, the body cannot effectively excrete excess magnesium. This increases the risk of developing hypermagnesemia, a magnesium overdose, which can be dangerous.

As a key component of hard water, high magnesium levels lead to limescale buildup in pipes and appliances. This reduces efficiency, lowers water pressure, and can cause damage to equipment like water heaters and dishwashers over time.

Yes, high concentrations of magnesium can give drinking water an unpleasant, bitter, or metallic taste. The salts can also make the water appear cloudy.

High magnesium water can make soap less effective, leaving a scum on the skin. While research is mixed, some studies have suggested a link between hard water and aggravated symptoms of atopic dermatitis (eczema).

The most common and effective method is a water softener, which uses an ion exchange process to replace magnesium and calcium ions with sodium or potassium ions. Other options include reverse osmosis systems for drinking water.

It is rare for healthy individuals to get too much magnesium from food alone, as the kidneys effectively remove the excess. The risk of magnesium toxicity primarily arises from high-dose supplements or medications, or from consuming excessive amounts in combination with pre-existing kidney issues.