What is the most appropriate next step in management?

A 17-year-old boy with type 1 diabetes mellitus was admitted with diabetic ketoacidosis precipitated by a recent viral illness.

Investigations on admission:

random plasma glucose15.0 mmol/L

arterial blood gases, breathing air:

pH7.07 (7.35C7.45)

H+85 nmol/L (35C45)

Investigations after initial treatment with fluids, insulin and potassium 7 h after admission:

random plasma glucose4.0 mmol/L

serum bicarbonate10 mmol/L (20C28)

At this stage, he was being given infusions of insulin (1 U/h) and glucose 5% (100 mL/h).

What is the most appropriate next step in management?
A . continue current regimen
B . continue current regimen but encourage oral carbohydrate intake
C . continue insulin infusion and change glucose to a higher concentration
D . give intravenous sodium bicarbonate
E . stop insulin infusion if glucose falls any further, then repeat plasma glucose in 15 min