What laboratory investigations are essential for confirming a diagnosis of HHS in primary care?

To confirm a diagnosis of hyperosmolar hyperglycaemic state (HHS) in primary care, essential laboratory investigations include measurement of plasma glucose, plasma osmolality, serum electrolytes (particularly sodium and potassium), urea, and creatinine concentrations. Additionally, assessment of venous blood acid–base status is important to differentiate HHS from diabetic ketoacidosis (DKA), as HHS typically presents without significant acidosis. Blood ketone measurement may also be useful to exclude ketoacidosis. These tests help confirm severe hyperglycaemia, dehydration, and electrolyte imbalances characteristic of HHS, guiding urgent referral and management decisions.