| ICD9 = | ICDO = | Image = Ca-TableImage.png | Caption = Calcium | OMIM = | OMIM_mult = | MedlinePlus = | eMedicineSubj = emerg | eMedicineTopic = 271 | DiseasesDB = 6412 | MeshID = D006996 | }} In medicine, hypocalcemia's the presence of low serum calcium levels in the blood, usually taken as less than 2.1 mmol/L or 9 mg/dl or an ionized calcium level mm of less than 1.1 mmol/L (4.5 mg/dL). It's a type of electrolyte disturbance. In the blood, about half of all calcium's bound to proteins suc… (More on Hypocalcaemia)