Answer:
According to the Physician's order, the amount of Calcitriol the nurse should administer is 1 ml.
Step-by-step explanation:
The presentation of the available Calcitriol is 1 mcg/ml, so the indication of 0.001 mg needed by a patient is equivalent to 1 ml, due to 
- 1 mg = 1000 mcg 
- 0.001 mg = 1 mcg 
The dose of 0.001 mg of Calcitriol is equal to say 1mcg of the drug, which is contained in 1 ml. 
Calcitriol is a drug that helps regulate calcium by acting on the synthesis of parathyroid hormone.