Hi, One of the side effects of all insulin (Including Lantus) is low potassium, which may cause leg spasms/cramps. Diabetes may also cause (particularly patient with poorly controlled sugar-levels) symptoms of diabetic neuropathy (motor type) due to damage to motor nerve roots. Damage to the arteries due to diabetes will cause less blood supply to the organ and hence cramps. High sugar levels when cleared from the body will also result in reduced levels of electrolytes due to excessive clearance of electrolytes along with clearance of sugar. It will also cause cramps. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician