Final answer:
In a patient diagnosed with diabetic ketoacidosis, the essential laboratory value to monitor is Potassium (K).
Step-by-step explanation:
In a patient diagnosed with diabetic ketoacidosis, the essential laboratory value to monitor is Potassium (K). When the body is in a state of ketoacidosis, insulin is lacking and glucose cannot be utilized by cells. This leads to the release of fatty acids and an overproduction of ketone bodies, causing an increase in blood acidity. Potassium levels can be significantly affected by this imbalance and should be closely monitored to prevent complications.