A technologist is confused by the serum calcium level of 4.5 mg/dL (reference interval 8.6 - 10.4 mg/dL) she obtains on a sample. She reruns the sample, and the results check as 4.5 mg/dL. There is no previous result on this patient, and the only other tests ordered are a complete blood count (CBC) and vitamin D.
What should her investigation include?
