A Client Having Severe Allergy Symptoms Has Received Several Doses

A client having severe allergy symptoms has received several doses of IV antihistamines.What action by the nurse is most important?

A) Assess the client's bedside glucose reading.
B) Instruct the client not to get up without help.
C) Monitor the client frequently for tachycardia.
D) Record the client's intake, output, and weight.