Is magnesium 500mg too much?

Magnesium is an important mineral that plays a role in over 300 enzyme reactions in the body. It helps regulate muscle and nerve function, blood sugar levels, blood pressure, and bone health. The recommended daily allowance (RDA) for magnesium is 310-420 mg for adults depending on age and gender.

Quick answers

– The recommended upper limit for magnesium from supplements or medications is 350 mg per day.

– Taking 500 mg of magnesium daily from supplements may cause diarrhea or other gastrointestinal side effects.

– Too much magnesium from supplements can result in dangerous electrolyte abnormalities.

– Food sources of magnesium like whole grains, nuts, leafy greens are safer ways to increase magnesium intake.

Is 500 mg of magnesium too much?

In short, yes, 500 mg daily is considered too much magnesium from supplements. The recommended upper limit for magnesium intake from supplements or medications is 350 mg per day for adults. Exceeding this amount regularly can lead to adverse effects.

The tolerable upper intake level (UL) for magnesium represents the maximum amount that can be taken daily without increased risk of harm or adverse health effects. While magnesium is an essential mineral, taking high doses from supplements may cause problems.

Potential risks and side effects

Some potential risks and side effects of getting 500 mg of magnesium daily from supplements can include:

  • Diarrhea
  • Abdominal cramping or discomfort
  • Nausea
  • Muscle weakness
  • Irregular heartbeat
  • Low blood pressure
  • Electrolyte imbalances

The most common side effect is loose stools or diarrhea. Magnesium acts as an osmotic laxative, drawing water into the intestines to stimulate evacuation of the bowels. Too much can lead to urgent, watery diarrhea.

Nausea, cramping, and abdominal discomfort are also fairly common when magnesium intake is too high. Magnesium may also interact with certain medications, including antibiotics and blood pressure medications.

Very high doses can potentially cause dangerously low calcium, potassium, or sodium levels. Magnesium competes with calcium for absorption, so excess magnesium can deplete calcium stores. It also interacts with potassium, causing excessive urination of potassium.

Recommended magnesium intake

The recommended dietary allowance (RDA) for magnesium is:

  • Men age 19-30: 400 mg per day
  • Men age 31+: 420 mg per day
  • Women age 19-30: 310 mg per day
  • Women age 31+: 320 mg per day

As you can see, the RDA is significantly lower than 500 mg. While the RDA represents the amount needed to meet the needs of 97-98% of healthy individuals, even levels above the RDA are not necessarily harmful.

However, the upper limit of 350 mg from supplements exists for a reason. Only consume higher amounts under medical supervision.

Food sources of magnesium

It’s typically preferable to get magnesium from food sources rather than supplements whenever possible. Foods high in magnesium include:

Food Magnesium per serving
Almonds, 1 ounce 80 mg
Spinach, 1⁄2 cup cooked 75 mg
Cashews, 1 ounce 74 mg
Edamame, 1⁄2 cup 50 mg
Black beans, 1⁄2 cup cooked 60 mg
Avocado, 1 medium 44 mg
Salmon, 3 ounces 26 mg
Banana, 1 medium 32 mg
Dark chocolate, 1 square 23 mg

Focusing on incorporating magnesium-rich foods like nuts, seeds, legumes, leafy greens, whole grains, and fatty fish can help provide adequate magnesium intake without the need for high-dose supplements.

When magnesium supplements may be appropriate

For certain people, magnesium supplements may be appropriate and beneficial when taken correctly under medical guidance. Potential situations when magnesium supplements may help include:

  • Confirmed magnesium deficiency due to a medical condition
  • Malabsorption conditions like celiac or inflammatory bowel disease
  • Type 2 diabetes
  • Congestive heart failure
  • Hypertension
  • Migraine headaches
  • Leg cramps in pregnancy
  • Increasing magnesium status after consulting with a doctor

In these cases, proper dosing of magnesium supplements can help correct deficiencies or provide therapeutic benefits. However, it’s important to use only the amount recommended for your specific health needs.

Forms of magnesium supplements

There are several forms of magnesium supplements available, including:

  • Magnesium oxide: often used as laxative but has poor bioavailability
  • Magnesium citrate: highly bioavailable and readily absorbed
  • Magnesium glycinate: well-absorbed and gentle on the stomach
  • Magnesium chloride: easily absorbed and topical forms available
  • Magnesium threonate: crosses the blood-brain barrier

The type of magnesium supplement determines the actual elemental magnesium content as well as absorption and tolerance. Magnesium citrate, glycinate, and chloride tend to have better bioavailability than magnesium oxide.

Recommended dosing

When magnesium supplements are used therapeutically, the dosage should be personalized based on the individual’s health condition, age, and other factors.

For deficiency: Doses range from 125-350 mg daily in divided doses, with higher end doses used short-term then reduced once levels improve.

For high blood pressure: 365-450 mg daily has been used in studies, under medical supervision.

For leg cramps in pregnancy: 360 mg daily has been used safely.

For chronic migraines: 400-500 mg has been used carefully as a preventive treatment.

For diabetes: Doses up to 500 mg divided twice daily along with vitamin D have been studied for improving insulin sensitivity and glucose control.

Again, it’s very important to only take higher doses of magnesium supplements under the guidance of a knowledgeable doctor or dietitian.

Testing your magnesium levels

Blood tests are available to check magnesium levels, although they have limitations. Less than 1% of the body’s magnesium is found in the blood, so blood levels don’t necessarily reflect total body stores.

One test is the serum magnesium test, which measures the amount of magnesium in the blood serum. Normal ranges are generally 0.75-0.95 mmol/L.

The red blood cell magnesium test can provide a better picture of long-term magnesium levels. Normal ranges are 1.7-2.55 mmol/L.

These tests along with medical evaluation can help determine if you are deficient and may benefit from magnesium supplementation.

Signs of magnesium deficiency

Some signs and symptoms that may indicate magnesium deficiency include:

  • Muscle twitches, tremors, or convulsions
  • Muscle cramps or tension
  • High blood pressure
  • Irregular heartbeat
  • Headaches and migraines
  • Fatigue and weakness
  • Restless sleep
  • Anxiety or irritability
  • Low calcium or potassium levels

Chronic diseases, medications, poor diet, malabsorption disorders, and alcohol abuse can increase the risk of magnesium deficiency. Deficiency is rare in healthy individuals who eat a balanced diet.

Sources of magnesium overdose

Magnesium overdose is almost always caused by overuse of magnesium supplements. Getting excessive magnesium from food alone is very rare.

Situations that could lead to magnesium overdose include:

  • Taking more than 350 mg daily without medical oversight
  • Using multiple types of magnesium supplements
  • Kidney dysfunction reducing magnesium excretion
  • Using magnesium supplements long-term without periodic lab testing
  • Improperly formulated or mislabeled magnesium supplements

Magnesium supplements may also interact with medications that can increase levels, including diuretics, proton pump inhibitors, and calcium channel blockers.

Toxicity symptoms

Signs of potentially harmful magnesium toxicity include:

  • Diarrhea
  • Nausea and vomiting
  • Abdominal pain
  • Confusion
  • Irregular heartbeat
  • Muscle weakness
  • Difficulty breathing
  • Low blood pressure
  • Coma in severe cases

High magnesium can be fatal in extreme toxicity. Seek immediate medical attention if you experience concerning symptoms of magnesium overdose like weakness, breathing problems, chest pain, or arrhythmias.

Treatment for high magnesium

Treatment depends on the severity of magnesium toxicity. Options may include:

  • Stopping supplemental magnesium
  • Hydration to flush out excess magnesium
  • Medications to bind magnesium in the digestive tract
  • Intravenous calcium to counteract magnesium levels
  • Dialysis in severe kidney failure
  • Ventilator support for respiratory paralysis

Most cases involving mild symptoms can be managed with hydration, stopping oral magnesium, and monitoring. Severe toxicity requires intensive treatment.

Populations at higher risk

Certain people are more susceptible to magnesium toxicity and should be especially cautious with dosing:

  • Individuals with kidney dysfunction
  • Older adults
  • People taking medications that interact with magnesium
  • People with myasthenia gravis or other neuromuscular disorders
  • Infants and young children

Kidney impairment reduces the body’s ability to excrete excess magnesium. Older adults often have decreased kidney function. Babies are smaller with immature kidneys and lower magnesium requirements.

Safety precautions

To use magnesium supplements safely:

  • Consult your doctor before starting to confirm appropriate dosing.
  • Read dosage instructions carefully.
  • Increase intake gradually if needed.
  • Avoid exceeding 350 mg per day from supplements.
  • Use for limited time periods unless advised otherwise.
  • Inform your doctor of any side effects.
  • Notify your doctor of any medications or supplements you take.
  • Get periodic lab tests if using long-term.
  • Contact your doctor about concerning symptoms.

Checking with your doctor before using magnesium supplements, following dosing instructions, and monitoring your health can help prevent adverse effects.


In summary, experts caution against regularly getting 500 mg of magnesium per day from supplements. This exceeds the recommended upper limit of 350 mg and may increase the risk of diarrhea, nausea, muscle weakness, heart arrhythmias, electrolyte abnormalities, and more.

Food sources of magnesium like leafy greens, nuts, whole grains, legumes, and fatty fish are great options that are not associated with toxicity. When used properly under medical supervision, magnesium supplements can also be appropriate and beneficial for some individuals. But it’s best to use the minimal effective dose.

If you have symptoms of a magnesium deficiency or feel you could benefit from more magnesium, have an open discussion with your healthcare provider. They can recommend the safest way to optimize your magnesium intake for health if needed.

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