[3] Symptoms include tremor, poor coordination, muscle spasms, loss of appetite, personality changes, and nystagmus.

[1] Causes include low dietary intake, alcoholism, diarrhea, increased urinary loss, and poor absorption from the intestines.

[2] Deficiency of magnesium can cause tiredness, generalized weakness, muscle cramps, abnormal heart rhythms, increased irritability of the nervous system with tremors, paresthesias, palpitations, low potassium levels in the blood, hypoparathyroidism which might result in low calcium levels in the blood, chondrocalcinosis, spasticity and tetany, migraines, epileptic seizures,[7] basal ganglia calcifications[8] and in extreme and prolonged cases coma, intellectual disability or death.

[9] Magnesium deficiency is strongly associated with and appears to contribute to obesity, insulin resistance, metabolic syndrome, and type 2 diabetes, although the causal mechanism is not fully understood.

Poor dietary intake of magnesium has become an increasingly important factor: many people consume diets high in refined foods such as white bread and polished rice which have been stripped of magnesium-rich plant fiber.

Low magnesium intake over time can increase the risk of illnesses, including high blood pressure and heart disease, diabetes mellitus type 2, osteoporosis, and migraines.

[25] The inhibition of the sodium-potassium pump results in more potassium remaining in the extracellular space (interstitial fluid and plasma).

[32] Magnesium deficiency is frequently observed in people with type 2 diabetes mellitus, with an estimated prevalence ranging between 11 and 48%.

[34] Magnesium deficiency is strongly associated with high glucose and insulin resistance, which indicate that it is common in poorly controlled diabetes.

[35] Patients with type 2 diabetes and a magnesium deficiency have a higher risk of heart failure, atrial fibrillation, and microvascular complications.

[37][38][39] A 2016 meta-analysis not restricted to diabetic subjects found that increasing dietary magnesium intake, while associated with a reduced risk of stroke, heart failure, diabetes, and all-cause mortality, was not clearly associated with lower risk of coronary heart disease (CHD) or total cardiovascular disease (CVD).

[40] Magnesium-rich foods include cereals, green vegetables (with magnesium being a main component of chlorophyll), beans, and nuts.

[25] Inside cells, 90-95% of magnesium is bound to ligands, including ATP, ADP, citrate, other proteins, and nucleic acids.

[25] 70% of magnesium is reabsorbed in the thick ascending limb of the loop of Henle where claudins 16 and 19 form the channels to allow for reabsorption.

[44] Other changes may include prolonged PR interval, ST segment depression, flipped T waves, and long QRS duration.

[48] Intravenous magnesium sulfate (MgSO4) can be given in response to heart arrhythmias to correct for hypokalemia, preventing pre-eclampsia, and has been suggested as having potential use in asthma.

[54] Excess potassium, generally due to fertilizers, further aggravates the stress from magnesium deficiency,[55] as does aluminium toxicity.

This causes the main symptom of magnesium deficiency, interveinal chlorosis, or yellowing between leaf veins, which stay green, giving the leaves a marbled appearance.

Adding Epsom salts (as a solution of 25 grams per liter or 4 oz per gal) or crushed dolomitic limestone to the soil can rectify magnesium deficiencies.

An organic treatment is to apply compost mulch, which can prevent leaching during excessive rainfall and provide plants with sufficient amounts of nutrients, including magnesium.