Diagnostic Criteria for DKA by Severity
Diabetic ketoacidosis (DKA) is an anion gap metabolic acidosis with ketosis driven by absolute or relative insulin deficiency. Severity is graded—mild, moderate, or severe—primarily by the degree of acidosis (arterial pH and serum bicarbonate) and mental status, not by the glucose level, which stays elevated across all grades. Recognizing this severity framework guides monitoring intensity and reminds you that the target of therapy is closing the anion gap, not merely normalizing glucose.
Mild DKA
Glucose is >250 mg/dL, arterial pH is 7.25–7.30, and serum bicarbonate is 15–18 mEq/L. The anion gap is >10 and ketones are positive. Crucially, the patient is alert—preserved mental status is the hallmark of mild disease. This is the least acidotic category and reflects early or well-compensated ketoacidosis.
Moderate DKA
Glucose remains >250 mg/dL, but acidosis has worsened: arterial pH falls to 7.00–7.24 and serum bicarbonate drops to 10–15 mEq/L. The anion gap is >12 and ketones are positive. Mental status is classified as alert/drowsy—it may still be preserved or beginning to decline, so an alert patient can absolutely meet biochemical criteria for moderate DKA. The worsening acidosis, not the mental status alone, drives the closer monitoring this grade warrants.
Severe DKA
Glucose is still >250 mg/dL, but the acidosis is profound: arterial pH is <7.00 and serum bicarbonate is <10 mEq/L. The anion gap is >12 and ketones are positive. The patient is obtunded or comatose (stupor/coma). This is the most dangerous grade and demands intensive monitoring and resuscitation.
How the Parameters Track Severity
Glucose (>250 mg/dL) and positive ketones are constant across all three grades—they establish that DKA is present but do not grade it. Severity is driven by the depth of acidosis: pH descends stepwise (7.25–7.30 → 7.00–7.24 → <7.00) and bicarbonate falls in parallel (15–18 → 10–15 → <10 mEq/L). Mental status trends with this progression: alert (mild), alert/drowsy (moderate), then stupor/coma (severe). Note the overlap—an alert patient may still have moderate biochemical DKA, so use pH and bicarbonate to grade rather than mental status alone. The anion gap is >10 in mild disease and >12 in moderate and severe disease.
High-yield
- DKA is an anion gap metabolic acidosis with ketosis—glucose >250 mg/dL and positive ketones in every severity grade.
- Severity is defined by acidosis (pH and bicarbonate) and mental status, NOT by the glucose value.
- pH thresholds: mild 7.25–7.30, moderate 7.00–7.24, severe <7.00.
- Serum bicarbonate thresholds: mild 15–18, moderate 10–15, severe <10 mEq/L.
- Mental status progression: alert (mild) → alert/drowsy (moderate) → stupor/coma (severe)—note that moderate DKA can still present with an alert patient.
- Euglycemic DKA—acidosis and ketosis with near-normal glucose—can occur with SGLT2 inhibitors; treat as DKA despite normal glucose.
- Continue the insulin drip until the anion gap closes, not just until glucose normalizes.
- Precipitants (the I's): Infection (most common), Insulin omission, Infarction, Intoxication, Iatrogenic (steroids), Initial presentation of type 1.
- Classic features: Kussmaul respirations, fruity (acetone) breath, nausea/vomiting/abdominal pain, polyuria/polydipsia.
Pitfalls
- Grading DKA by glucose level—glucose is >250 mg/dL in all grades and does not determine severity.
- Assuming an alert patient cannot have moderate DKA—moderate disease is classified as alert/drowsy, so an alert patient with pH 7.00–7.24 and bicarbonate 10–15 mEq/L still qualifies.
- Being fooled by near-normal glucose in euglycemic DKA (SGLT2 inhibitors) and missing the diagnosis.
- Stopping the insulin drip when glucose normalizes instead of waiting for the anion gap to close.
- Forgetting to add dextrose when glucose falls <200 mg/dL while insulin continues to close the gap.
- Giving insulin before checking potassium—if K+ <3.3, hold insulin and replace potassium first because insulin drives K+ into cells and can precipitate dangerous hypokalemia.
- Assuming a normal or high serum potassium means adequate stores—total body potassium is LOW even when serum K+ is high from acidosis.
- Routinely giving bicarbonate—it is rarely indicated and reserved for very severe acidosis (pH <6.9).
Clinical pearls
- Mental status is a bedside clue to acidosis, but grade DKA by pH and bicarbonate—an alert patient can still have moderate disease.
- In DKA, serum K+ may be high initially but total body K+ is depleted—expect a precipitous drop once insulin starts.
- Close the gap, don't just chase the glucose.
- Don't let a glucose of 180 mg/dL with strong ketones and low pH talk you out of DKA on an SGLT2 inhibitor.
- Fluids are the first priority in DKA resuscitation.
Frequently asked
What single parameter is constant across all DKA severities and therefore cannot be used for grading?
Glucose. It is >250 mg/dL in mild, moderate, and severe DKA, so it establishes the diagnosis but does not determine severity. Ketones are also positive in all grades.
Which parameters actually define DKA severity?
Arterial pH, serum bicarbonate, and mental status. pH and bicarbonate quantify the acidosis, and mental status (alert → alert/drowsy → stupor/coma) reflects its clinical severity.
How do the pH and bicarbonate cutoffs separate the three grades?
Mild: pH 7.25–7.30, bicarbonate 15–18 mEq/L. Moderate: pH 7.00–7.24, bicarbonate 10–15 mEq/L. Severe: pH <7.00, bicarbonate <10 mEq/L.
Can a fully alert patient have moderate DKA?
Yes. Moderate DKA mental status is classified as alert/drowsy, so an alert patient can still meet moderate criteria if the pH is 7.00–7.24 and bicarbonate is 10–15 mEq/L. Grade by the biochemistry—not by mental status alone.
What is euglycemic DKA and why does it matter for severity assessment?
It is DKA with acidosis and positive ketones but near-normal glucose, classically triggered by SGLT2 inhibitors. It matters because relying on glucose would cause you to miss it—diagnosis and severity still rest on pH, bicarbonate, ketones, and mental status. Treat it exactly like DKA with fluids, insulin, and potassium monitoring.
When should you stop the insulin infusion in DKA?
When the anion gap closes—not when glucose normalizes. Add dextrose once glucose falls below 200 mg/dL to prevent hypoglycemia while insulin continues to resolve the ketosis.
Why must potassium be checked before starting insulin?
Insulin drives potassium into cells and can cause a precipitous drop. If K+ is <3.3, hold insulin and replace potassium first; if 3.3–5.3, give insulin with potassium; if >5.3, give insulin and recheck. Total body potassium is low even when serum K+ appears high from acidosis.
Is bicarbonate therapy part of standard DKA management?
No. Bicarbonate is rarely indicated in DKA and is reserved for very severe acidosis (pH <6.9). Fluids, insulin, and potassium management are the core of therapy.
Turn this into reasoning you can use on exam day — practice Diagnostic Criteria for DKA by Severity on branching cases where your decisions shape the patient.