Common symptoms of mild-moderate deficiency are anxiety, depression, fatigue, insomnia, irritability, panic attacks, muscle cramps or twitches, hypertension and headaches.
Magnesium supplements come in a wide range of forms and vary in their ability to be absorbed and utilized by the body. Magnesium citrate and oxide are a lower cost form and tend to cause more digestive upset or diarrhea at lower doses, whereas magnesium glycinate/bisglycinate and other amino acid chelates are more absorbable and effective to correct deficiency. Magnesium has been shown to be effective for conditions such as migraine prophylaxis, hypertension, PMS, restless leg syndrome and sleep disturbances. I have also used it clinically to reduce muscle cramps and pain.
Magnesium does interact with certain medications so it is important to consult a healthcare professional prior to starting any supplementation.