Workup to confirm diagnosis and search for possible inciting causes (e.g. infection, ACS)
CBC
BMP
Blood glucose
Serum ketones (e.g. beta-hydroxybutyrate and/or acetone)
Mag
Phos
VBG/ABG
Consider ECG, urinalysis, chest X-ray, blood cultures
Diagnosis is made based on the presence of acidosis (e.g. pH < 7.3) and ketonemia in the setting of diabetes (e.g. glucose >250mg/dl)
Blood Glucose
Capillary blood sugar >250mg/dL
Blood sugar may not be very elevated if there is impaired gluconeogenesis (eg liver failure, severe alcoholism) or patient is taking a SGLT-2 Inhibitor 
Elevated Anion Gap
Bicarb may be normal due to compensatory and contraction alkalosis so the elevated anion gap or ketonuria may be the only clues to the<unk> 
Serum ketones
Beta hydroxybutyrate will be elevated
Capillary blood sugar >250mg/dL
Blood sugar may not be very elevated if there is impaired gluconeogenesis (eg liver failure, severe alcoholism) or patient is taking a SGLT-2 Inhibitor 
Bicarb may be normal due to compensatory and contraction alkalosis so the elevated anion gap or ketonuria may be the only clues to the<unk> 
Beta hydroxybutyrate will be elevated
No need to perform Arterial blood gas. Venous blood gas is sufficient
Difference in pH from VBG vs ABG  will be ±0.02pH units 
Urinalysis may be a useful screening test early in<unk> , if serum ketones not available
However, may give a false negative for ketones later in<unk> , as acetoacetate is converted to beta-hydroxybutyrate the urinary ketones may turn negative
However, may give a false negative for ketones later in<unk> , as acetoacetate is converted to beta-hydroxybutyrate the urinary ketones may turn negative
Strongly consider capnography for respiratory distress
ETCO2 can be used for bedside assessment of<unk>  in pts with glucose>550
An ETCO2 of ≥35 is 100% sensitive to rule out<unk> 
An ETCO2 of ≤21 is 100% specific to diagnosis<unk> 
An ETCO2 of ≥35 is 100% sensitive to rule out<unk> 
An ETCO2 of ≤21 is 100% specific to diagnosis<unk>
Diabetic ketoacidosis
Insulin or oral hypoglycemic medication non-compliance 
Alcoholic ketoacidosis
Infection
Starvation ketoacidosis
Cardiac Ischemia
Cerebral edema in DKA
Intra-abdominal infections