Is it normal to feel nauseous after taking magnesium?

December 19, 2025 •

4 min read

Over half of adults in the United States may consume less than the daily recommended amount of magnesium, leading some to take supplements where they might encounter gastrointestinal side effects. As a result, it is not uncommon to feel nauseous after taking magnesium, though the cause is often manageable with a few simple adjustments.

Quick Summary

It is normal to experience nausea or digestive upset from magnesium supplements, a common side effect of high doses or certain forms. Solutions include taking a lower dose, changing the supplement type, or consuming it with food to reduce irritation.

Key Points

Nausea is Common: Feeling nauseous after taking magnesium is a common side effect, especially with higher doses or certain supplement types.
Poor Absorption Causes Issues: Less bioavailable magnesium forms like oxide can remain in the digestive tract, drawing water and causing gastrointestinal discomfort.
Dosage is Key: High doses, particularly above the 350mg UL for supplements, are more likely to cause nausea and other digestive issues.
Take with Food: To reduce stomach irritation and improve absorption, always take magnesium with a meal or snack.
Choose a Better Form: Switching to a more easily absorbed and gentler form, like magnesium glycinate or malate, can significantly reduce the risk of nausea.
Start Low and Split Doses: Beginning with a smaller dose and dividing your daily intake into multiple servings can help your body adjust and minimize side effects.
Monitor for Severe Symptoms: Persistent or severe symptoms, such as muscle weakness or irregular heartbeat, may indicate magnesium toxicity and require immediate medical attention.

Understanding Magnesium-Related Nausea

Magnesium is an essential mineral involved in over 300 biochemical reactions in the body, supporting everything from nerve and muscle function to heart health. For this reason, many people turn to supplements to increase their intake. However, for a significant portion of users, this can lead to unwanted digestive side effects, with nausea and diarrhea being among the most frequently reported issues. The root causes of this discomfort are typically related to the dose, the form of the supplement, and how it is consumed. By understanding these factors, you can take steps to minimize the risk of stomach upset and enjoy the benefits of supplementation without distress.

Why Your Magnesium Supplement Might Cause Nausea

Osmotic Effect and Poor Absorption

The most common reason for magnesium-induced nausea is the osmotic effect it has on the intestines. When the body cannot absorb all of the magnesium ingested, the unabsorbed portion remains in the bowel and draws water from the body's tissues. This influx of water softens the stool and can lead to diarrhea, stomach cramps, and the accompanying sensation of nausea. The forms of magnesium with the lowest bioavailability—meaning they are poorly absorbed—are the most likely culprits for this effect, as more of the mineral passes through the digestive tract undigested.

Excessive Dosage

Taking too high a dose of magnesium, particularly in a single sitting, significantly increases the likelihood of side effects like nausea. The Tolerable Upper Intake Level (UL) for supplemental magnesium is 350 mg for adults. Doses exceeding this amount are more prone to causing digestive distress as the body struggles to process the excess mineral. While your kidneys are capable of flushing out excess magnesium, an overload can overwhelm this process and cause a variety of side effects, including nausea.

Taking on an Empty Stomach

Just like many other supplements, magnesium can irritate the stomach lining when taken without food. Consuming your supplement with a meal or snack can help to buffer its effects on the stomach and slow down its transit through the digestive tract, which improves absorption and reduces the risk of side effects. Taking magnesium on an empty stomach, by contrast, can exacerbate gastrointestinal issues, especially with sensitive individuals or certain magnesium forms.

How to Prevent Magnesium-Related Nausea

Preventing nausea from magnesium is often a matter of fine-tuning your supplementation strategy. Consider the following adjustments:

Switch Your Magnesium Form: The type of magnesium salt used in a supplement is a major determinant of its gastrointestinal impact. If you are experiencing nausea, switching from a poorly absorbed form like magnesium oxide to a more bioavailable form may resolve the issue.
Reduce Your Dose: Start with a lower dose and increase it gradually over time. This allows your body to adjust to the supplement and can help identify the ideal dosage that provides benefits without causing side effects.
Take with Food: Always consume your magnesium supplement with a meal or snack. This simple change can make a significant difference in tolerability and absorption.
Divide Your Dosage: Instead of taking one large dose, split it into smaller amounts throughout the day. This reduces the concentration of magnesium in the digestive system at any one time, lowering the risk of osmotic effects.

Comparison of Common Magnesium Forms


Factor	Magnesium Oxide	Magnesium Citrate	Magnesium Glycinate	Magnesium Malate
Bioavailability	Poor; not well absorbed.	Good; well absorbed.	High; often considered one of the best absorbed.	High; excellent absorption.
Likelihood of Nausea	High, especially in large doses.	Moderate; may cause diarrhea in high doses.	Low; very gentle on the stomach.	Low; well-tolerated and gentle on the gut.
Common Use	Heartburn, indigestion, constipation relief.	General supplementation, mild constipation.	Relaxation, sleep support, anxiety reduction.	Muscle support, energy production.

When to Consult a Healthcare Provider

While mild nausea is often not a cause for concern, it is important to seek medical advice if your symptoms are severe or persistent. This is especially true if you have pre-existing health conditions, particularly kidney disease, which can impair your body's ability to excrete excess magnesium. Very high doses of magnesium (typically over 5,000 mg/day, but even above 350 mg can cause issues) can lead to magnesium toxicity, with severe symptoms such as muscle weakness, low blood pressure, confusion, and irregular heart rate. If you experience any of these serious side effects, stop taking the supplement and seek immediate medical attention.

For more detailed information on magnesium, consult authoritative resources such as the National Institutes of Health.(https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/)

Conclusion

In summary, it is quite normal to experience nausea after taking a magnesium supplement, with the main triggers being the dose, the form, and whether it's taken on an empty stomach. By strategically choosing a highly bioavailable and gentle form, starting with a low dose, and ensuring you take it with food, most individuals can successfully manage or eliminate this side effect. If discomfort persists or you have underlying health concerns, always consult with a healthcare professional to determine the best approach for your needs.

Frequently Asked Questions

Magnesium oxide is poorly absorbed by the body, meaning a larger portion of the supplement remains in the digestive tract. This unabsorbed magnesium draws water into the intestines, causing an osmotic effect that can lead to diarrhea, cramps, and nausea.

It is generally not recommended to take magnesium on an empty stomach, as it can cause irritation and increase the risk of nausea and diarrhea. Taking it with a meal or snack helps buffer the stomach and improves absorption.

Magnesium glycinate is often recommended for its high bioavailability and gentle effect on the digestive system, making it a great option for those who experience stomach sensitivity. Magnesium malate is also well-tolerated.

Yes, excessive doses of magnesium supplements, especially above the 350 mg Tolerable Upper Intake Level, are a primary cause of nausea, diarrhea, and other gastrointestinal side effects.

Mild nausea and other side effects typically resolve within a few hours of taking the supplement. However, if symptoms are severe or persist, it may be a sign of a larger issue and you should consult a doctor.

You should see a doctor if you experience persistent or severe symptoms, especially if accompanied by muscle weakness, lethargy, low blood pressure, or an irregular heart rate, as this could indicate magnesium toxicity.

Taking magnesium with a meal is more important than the time of day. However, for those with sensitivity, splitting the dose between morning and night meals may help minimize digestive upset.

Yes, magnesium citrate is known for its mild laxative effect. It is a well-absorbed form but can cause diarrhea, especially in higher doses, due to its ability to draw water into the intestines.