Side effects from increased magnesium intake are not common because the body removes excess amounts. Magnesium excess almost always occurs only when magnesium is supplemented as a medication.

Lack of magnesium (deficiency) is rare. The symptoms include:

• Hyperexcitability
• Muscle weakness
• Sleepiness

Deficiency of magnesium can occur in people who abuse alcohol or in those who absorb less magnesium due to:

• Burns
• Certain medications
• Low blood levels of calcium
• Problems absorbing nutrients from the intestinal tract (malabsorption)
• Surgery

Symptoms due to a lack of magnesium have three categories.

Early symptoms:

• Anorexia
• Apathy
• Confusion
• Fatigue
• Insomnia
• Irritability
• Muscle twitching
• Poor memory
• Reduced ability to learn

Moderate deficiency symptoms:

• Heart (cardiovascular) changes
• Rapid heartbeat

Severe deficiency:

• Continued muscle contraction
• Delirium
• Numbness
• Seeing or hearing things that aren't there (hallucinations)
• Tingling