Article Series

  1. Magnesium - Functions And Health Benefits
  2. Daily Magnesium Requirement
  3. Foods with Magnesium / Magnesium-Rich Foods
  4. Magnesium - Overdose & Excess

Related Articles

Magnesium - Overdose & Excess

Magnesium - Overdose & Excess
Table Of Contents
  1. Risk Groups
  2. Causes
  3. Signs Of Too Much Magnesium / Symptoms
  4. Consequences
  5. Detecting Magnesium Overdose
  6. Treatment
  7. Preventive Measures
  8. Maximum intake levels of magnesium supplements

The kidneys are able to excrete up to 100% (250 mmol per day) of the absorbed magnesium through urine 1 2. Hypermagnesemia with its corresponding symptoms is rare in individuals with normal kidney function 3. However, under certain conditions, magnesium can accumulate in the body. If there is consistently too much magnesium in the body (hypermagnesemia), it can impair muscle function.

In medical terminology, an excess of magnesium or high magnesium concentrations in the body are referred to as hypermagnesemia.

Risk Groups

The following groups can be affected by magnesium poisoning:

  • Patients with kidney disorders
  • Patients with gastrointestinal diseases
  • Dialysis patients (due to the use of magnesium-containing medications) 4 5
  • Preterm infants
  • Older individuals (due to incorrect use of medications or dietary supplements) 6


In most cases, the cause of magnesium excess is renal insufficiency 7 8. This leads to an increase in waste substances such as magnesium. Morbus Addison (adrenal cortex disease) can also be a cause.

An excess can occur even without severe renal insufficiency. Specifically, when there is a gastrointestinal disease present (such as ulcers, gastritis, ulcerative colitis, gastric volvulus) 9. This could be the cause of increased absorption of magnesium from food. Older individuals are particularly affected.

With the permanent use of magnesium-containing dietary supplements, an overdose of magnesium can occur. Medications such as antacids (neutralize stomach acid) and cathartics (moderate laxatives) that contain magnesium are often the cause of an overdose. 10 11 12 13 14 15. Magnesium-rich foods are rarely the cause of an excess.

Overdosing can occur through intravenous administration of magnesium.

Severe hypermagnesemia has also been observed in people who have consumed Dead Sea water 16. Additionally, continuous gargling with magnesium sulfate (Epsom salt) for halitosis (bad breath) led to severe magnesium excess resulting in coma 17.

Other causes may include 18 19 20 21:

  • Hypothyroidism (underactive thyroid)
  • Lithium therapy (reduced urinary excretion)
  • Disorder of calcium metabolism (milk-alkali syndrome)
  • Familial hypercalcemia (disorder of calcium metabolism)
  • Severe burns (leading to shifts from intracellular to extracellular magnesium concentrations)
  • In the treatment of eclampsia, an excess can be triggered
  • Parenteral and enteral nutrition
  • In rare cases: acidosis (metabolic acidification of the blood)

Signs Of Too Much Magnesium / Symptoms

Symptoms of magnesium overdose and excess can include 22 23 24 25 26:

  • Low pulse
  • Drop in blood pressure
  • Nausea
  • Vomiting
  • Loss of tendon reflexes
  • Muscle fatigue
  • Disturbances in movement coordination (ataxia)
  • Itching (pruritus)
  • Redness of the skin
  • Confusion
  • Drowsiness / somnolence (disorder of consciousness; sleepy state)
  • Lethargy
  • Cardiac arrhythmias
  • Respiratory difficulties
  • Paralysis

The symptoms are exacerbated by a calcium deficiency 27.


A magnesium excess and magnesium poisoning most commonly cause vasodilation (widening of blood vessels) and neuromuscular symptoms 28. The latter occur due to neuromuscular blockade, where the release of presynaptic acetylcholine (neurotransmitter that mediates muscle contractions) is inhibited 29. The central nervous system can be influenced by an excess of magnesium, disrupting impulse transmission (including impulse conduction speed) 30. Resulting symptoms include paralysis such as paralytic ileus (intestinal paralysis) and respiratory difficulties 31 32.

An excess of magnesium can lead to neurological and cardiological consequences. These include lethargy, confusion, changes in heart rhythm (such as prolongation of the PR interval), heart rate below 60 beats per minute (bradycardia), coma, complete heart block (interruption of cardiac activity), and cardiac arrest. 33 34 35 36 37 38. In severe cases, magnesium overdose can lead to death. For example, a 75-year-old woman died as a result of orally consuming magnesium chloride 39.

In addition, reduced magnesium excretion is associated with an increased incidence of ischemic heart disease (heart circulation disorder) 40.

A magnesium overdose leads to a decrease in calcium concentrations (hypocalcemia / calcium deficiency) in the serum 41. The reduced calcium levels occur due to a decreased release of thyroid hormones 42. Additionally, scientists suspect that elevated magnesium levels alter the intracellular concentration of calcium 43. This could impair bone metabolism and osteoblast activity, leading to bone disorders 44 45. Osteoblasts are necessary for bone formation.

Detecting Magnesium Overdose

By measuring magnesium concentrations in the serum, an excess can be easily detected. Furthermore, heart activities should be observed as well. In this case, conclusions about an illness can also be drawn. Additionally, calcium levels should also be checked as a calcium deficiency often occurs simultaneously with excess magnesium.

The following table provides information on normal and elevated magnesium levels:

ConditionSerum Magnesium
Normal 1.8-2.8 mg/dl (0.75-1.15 mmol/l)

0.54–0.67 mmol/l (ionized Mg concentration)
Magnesium Excess > 2.8 mg/dl (1.15 mmol/l)

the first symptoms occur at 2.0 mmol/l (4.86 mg/dl) or higher


Treatment is performed depending on the cause.

First, the intake of magnesium should be reduced or minimized as much as possible. In individuals with normal kidney function, this excess is already resolved.

In addition, the excretion of magnesium can be induced through diuretic medications (diuretics) and furosemide (causes fluid elimination) if necessary, along with additional water intake 46 47. However, caution is advised here as diuretics also increase calcium excretion 48. Simultaneous measurement of calcium concentrations and monitoring of heart activity using EKG may be useful during the treatment phase.

In patients with symptomatic hypermagnesemia, in addition to reducing magnesium intake, intravenous administration of calcium at dosages of 100 to 200 mg over 1-2 hours should be considered 49. This temporarily improves symptoms.

To quickly counteract the symptoms of severe magnesium poisoning, 1g of calcium in the form of calcium gluconate can be administered intravenously. 50 51. Subsequently, an infusion of 100-150mg of calcium should be administered over a period of 5-10 minutes. It may also be beneficial to provide glucose and insulin to transport magnesium into the cells.

If there is kidney disease or a massive overdose, blood washing (dialysis) may be necessary. 52 53.

Preventive Measures

High doses of magnesium salts should be avoided in patients with renal failure. 54 55. In general, magnesium levels should be regularly monitored in patients with kidney disease.

Maximum intake levels of magnesium supplements

To prevent magnesium overdose with magnesium salt supplements such as magnesium chloride, magnesium sulfate, magnesium aspartate, and magnesium lactate, the following daily maximum amounts should not be exceeded. 56:

Gender and Age GroupAmount in mg
Over 18 years 350
Over 18 years 350
Pregnant 350
Breastfeeding 350
0 to 12 months N/A
1 to 3 years 65
4 to 8 years 110
9 to 19 years 350