How to check for dka
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"diabetic ketoacidosis" AND diagnosis
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Here is a thorough answer on how to check for DKA, drawn from Rosen's Emergency Medicine and Goldman-Cecil Medicine.
How to Check for DKA (Diabetic Ketoacidosis)
The Core Diagnostic Triad
The three fundamental biochemical features required for diagnosis are:
- Hyperglycemia - Blood glucose typically >250 mg/dL (though it can vary widely, even approaching normal in rare cases)
- Ketosis - Urine ketones 2+ or more, OR serum beta-hydroxybutyrate ≥3.0 mmol/L
- Acidosis - Arterial or venous pH <7.3, and/or serum bicarbonate <18 mmol/L
Step-by-Step Investigation
1. History and Clinical Clues
Look for:
- Polydipsia, polyuria, polyphagia, weight loss
- Nausea, vomiting, abdominal pain (present in ~50% of cases, especially children)
- Weakness, lethargy, reduced consciousness
- Known diabetes (but ~25% of DKA episodes occur in newly diagnosed patients)
- Precipitants: missed insulin, infection, acute coronary syndrome, stress
2. Physical Examination Signs
- Kussmaul breathing - deep, rapid respirations (respiratory compensation for metabolic acidosis)
- Fruity/acetone odor on the breath
- Tachycardia and orthostatic hypotension or frank hypotension
- Dry skin and mucous membranes (dehydration)
- Depressed mental status (in severe cases, coma)
- Elevated temperature suggests an underlying infection as precipitant
3. Essential Laboratory Tests
| Test | What to Expect in DKA |
|---|---|
| Blood glucose | Usually >250 mg/dL (sometimes >350 mg/dL; can be lower in euglycemic DKA) |
| Serum ketones / beta-hydroxybutyrate | Elevated; BHB is more reliable than nitroprusside strips |
| Urine ketones (dipstick) | 2+ or greater |
| Arterial or venous blood gas | pH <7.3; pCO2 low (respiratory compensation) |
| Serum bicarbonate | <18 mmol/L (severe: <10 mmol/L) |
| Anion gap | Elevated (calculated as Na - [Cl + HCO3]; normal ~12, elevated in DKA) |
| Serum electrolytes | Na+ often low (dilutional); K+ may appear normal/elevated but total body K is depleted |
| BUN/Creatinine | Often elevated (prerenal azotemia) |
| CBC | WBC often elevated - not necessarily infection; Hematocrit elevated (hemoconcentration) |
| Serum amylase | May be elevated - usually not pancreatic in origin; do not mistake for pancreatitis without other evidence |
4. Ketone Testing - Important Caveat
Nitroprusside-based urine/serum dipstick tests detect acetoacetate, but beta-hydroxybutyrate (BHB) - the predominant ketone in DKA - does NOT react with nitroprusside. This means dipstick ketones can be falsely low. Use point-of-care BHB meters (fingerstick beta-hydroxybutyrate) for a more accurate assessment when available; a value ≥3.0 mmol/L confirms significant ketosis.
5. Severity Classification (Rosen's / Goldman-Cecil)
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| pH | 7.20-7.30 | 7.10-7.20 | <7.10 |
| Bicarbonate | 15-18 | 10-15 | <10 |
| Mental status | Alert | Drowsy | Stupor/Coma |
Differentials to Rule Out
The anion gap acidosis in DKA must be distinguished from:
- Alcoholic ketoacidosis (patient may be euglycemic or hypoglycemic; often with alkalosis from vomiting)
- Starvation ketosis (mild, bicarbonate rarely <18)
- Lactic acidosis (e.g., from sepsis or metformin)
- Toxic ingestions (methanol, ethylene glycol, salicylates)
- Hyperosmolar Hyperglycemic State (HHS) - glucose is much higher (>700 mg/dL), but ketosis and acidosis are minimal because residual insulin suppresses lipolysis
Quick Summary
To check for DKA, obtain: blood glucose + blood gas (pH, bicarb) + ketones (preferably serum BHB) + electrolytes + anion gap. The diagnosis is confirmed when all three elements of the triad - high glucose, acidosis, and ketosis - are present together.
- Rosen's Emergency Medicine, p. 2542-2543
- Goldman-Cecil Medicine, p. 2484
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