Diabetic Ketoacidosis

Diabetic ketoacidosis (DKA) is an acute, life-threatening metabolic decompensation of diabetes defined by the triad of hyperglycaemia, ketonaemia/ketonuria, and high-anion-gap metabolic acidosis. It is the commonest hyperglycaemic emergency in type 1 diabetes and a perennially high-yield NEET PG topic, tested heavily on diagnostic cut-offs, the sequence of management (fluids → potassium → insulin), and the contrast with hyperosmolar hyperglycaemic state (HHS).

Definition & diagnostic criteria

DKA is biochemically defined by three simultaneous abnormalities. The classic ADA cut-offs are the most examined numbers in this topic.

Parameter	Cut-off for DKA
Plasma glucose	> 250 mg/dL (may be normal/low in euglycaemic DKA)
Arterial pH	< 7.30
Serum bicarbonate	< 18 mEq/L
Anion gap	> 10–12 (raised)
Ketones	Positive serum/urine; β-hydroxybutyrate ≥ 3 mmol/L

Severity is graded by pH and bicarbonate:

Severity	pH	HCO₃⁻ (mEq/L)	Mental status
Mild	7.25–7.30	15–18	Alert
Moderate	7.00–7.24	10–<15	Alert/drowsy
Severe	< 7.00	< 10	Stupor/coma

High-yield: The single most reliable biochemical marker of DKA resolution and severity is β-hydroxybutyrate (β-OHB), not acetoacetate. The nitroprusside (Acetest/Ketostix) reaction detects acetoacetate and acetone but NOT β-hydroxybutyrate — so early DKA, where β-OHB predominates, can give falsely low urine ketones, and paradoxically the urine ketone test may appear to worsen during recovery as β-OHB converts to acetoacetate.

Etiology & precipitants

DKA arises from absolute or relative insulin deficiency plus a rise in counter-regulatory (stress) hormones — glucagon, catecholamines, cortisol, and growth hormone. The classic precipitants are remembered as the 6 I's:

Mnemonic — "The 6 I's of DKA":

1. Infection (commonest precipitant overall — UTI, pneumonia)
2. Infarction (MI, stroke, mesenteric ischaemia)
3. Insulin omission / non-compliance (commonest in young type 1 patients)
4. Inaugural / first presentation of type 1 diabetes
5. Iatrogenic (steroids, thiazides, atypical antipsychotics, SGLT2 inhibitors → euglycaemic DKA)
6. Intoxication / Illness (alcohol, pancreatitis, pregnancy)

High-yield: SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) are the classic cause of euglycaemic DKA — ketoacidosis with glucose < 200–250 mg/dL because urinary glucose loss masks hyperglycaemia. Other euglycaemic causes: pregnancy, prolonged starvation, chronic liver disease, and heavy alcohol use.

Pathophysiology

The core defect is the high glucagon-to-insulin ratio. The cascade:

Insulin deficiency + ↑ counter-regulatory hormones → unrestrained lipolysis → free fatty acids reach the liver → β-oxidation → ketone bodies (β-hydroxybutyrate, acetoacetate, acetone) → metabolic acidosis.

Simultaneously, two parallel processes drive hyperglycaemia and volume depletion:

1. Hyperglycaemia pathway: Insulin lack + glucagon excess → ↑ gluconeogenesis + ↑ glycogenolysis + ↓ peripheral glucose uptake → hyperglycaemia.
2. Osmotic diuresis pathway: Glucose > renal threshold (~180 mg/dL) → glycosuria → osmotic diuresis → loss of water and electrolytes (Na⁺, K⁺, PO₄³⁻, Mg²⁺) → severe dehydration (deficit 5–7 L), hypovolaemia, prerenal azotaemia.

Why ketones cause acidosis: Acetoacetic and β-hydroxybutyric acids are strong organic acids that dissociate to release H⁺, consuming bicarbonate and producing a high-anion-gap metabolic acidosis (HAGMA).

The potassium paradox: Total body potassium is depleted (loss via osmotic diuresis, vomiting, secondary hyperaldosteronism), yet measured serum K⁺ is often normal or high at presentation. This is because acidosis and insulin deficiency drive K⁺ out of cells (transcellular shift). Once insulin and fluids are given, K⁺ rushes intracellularly and serum levels plummet — the basis of insulin-induced hypokalaemia.

Clinical features

Onset is typically rapid (< 24 hours), in contrast to the insidious HHS.

• Symptoms: Polyuria, polydipsia, weight loss, weakness, nausea, vomiting, abdominal pain (can mimic an acute abdomen — especially in children).
• Signs of dehydration: Dry mucous membranes, tachycardia, hypotension, reduced skin turgor.
• Kussmaul breathing: Deep, rapid, sighing respirations — respiratory compensation for metabolic acidosis (seen when pH < 7.2).
• Acetone breath: Fruity odour from exhaled acetone.
• Altered sensorium: Drowsiness to coma; coma correlates better with serum osmolality than with glucose or pH.

High-yield: Abdominal pain in DKA correlates with the severity of acidosis (typically with bicarbonate < 10). However, never assume abdominal pain is "just DKA" — always exclude a precipitating intra-abdominal cause, especially if it persists after correction.

Investigations

Investigation of choice for diagnosis/monitoring: Serum β-hydroxybutyrate (point-of-care or lab). Arterial/venous blood gas confirms acidosis.

Essential workup:

• Capillary + plasma glucose
• Venous/arterial blood gas — pH, HCO₃⁻ (venous pH is adequate and avoids arterial puncture; usually ~0.03 lower than arterial)
• Serum/capillary ketones (β-OHB preferred)
• Serum electrolytes — Na⁺ (calculate corrected Na⁺), K⁺, Cl⁻, HCO₃⁻; calculate anion gap
• Urea, creatinine (prerenal pattern)
• Serum osmolality (effective osmolality)
• CBC (leucocytosis common even without infection; > 25,000 suggests true infection), urinalysis, blood/urine cultures, CXR, ECG (precipitant + hyperkalaemia changes), septic screen
• HbA1c to gauge chronic control / new diagnosis

Key formulae (memorise):

• Anion gap = Na⁺ − (Cl⁻ + HCO₃⁻); normal 8–12 mEq/L.
• Corrected Na⁺ = measured Na⁺ + 1.6 (or 2.4) × [(glucose − 100)/100]. Hyperglycaemia causes dilutional pseudohyponatraemia.
• Effective serum osmolality = 2 × Na⁺ + (glucose/18). (Note: urea is excluded because it crosses cell membranes freely and is not osmotically "effective".)

High-yield: Initial measured serum sodium is usually low (pseudohyponatraemia) because glucose pulls water into the vascular space. Always correct it — a "normal" or high corrected sodium signals profound free-water deficit.

Management

The cornerstones are fluids, potassium, and insulin — in that order of priority. Treat the patient in a high-dependency/ICU setting with hourly monitoring.

Stepwise approach (the management flow):

Step 1 — IV fluids → Step 2 — Check & replace potassium → Step 3 — Insulin infusion → Step 4 — Switch fluid to dextrose when glucose ~200 → Step 5 — Treat precipitant & monitor for complications → Step 6 — Transition to subcutaneous insulin with overlap.

1. Fluid resuscitation (first priority)

• Start with isotonic 0.9% normal saline: ~1 L in the first hour (15–20 mL/kg), then titrate to haemodynamics.
• After initial resuscitation, assess corrected sodium: if normal/high → switch to 0.45% saline; if low → continue 0.9% saline.
• When plasma glucose reaches ~200–250 mg/dL, add 5% dextrose (often 5% dextrose in 0.45% saline) so that the insulin infusion can continue to clear ketones without causing hypoglycaemia.

High-yield: Fluids alone lower glucose substantially (by haemodilution, improved renal perfusion, ↓ counter-regulatory hormones) and partly correct acidosis. Always start fluids before insulin — giving insulin first to a hypovolaemic patient can precipitate circulatory collapse and dangerous hypokalaemia.

2. Potassium (the most exam-tested sequencing rule)

Serum K⁺ (mEq/L)	Action
< 3.3	Hold insulin. Give K⁺ (20–30 mEq/h) until K⁺ > 3.3, THEN start insulin
3.3 – 5.2	Give 20–30 mEq K⁺ in each litre of fluid; start insulin
> 5.2	Do not give K⁺; recheck every 2 h; start insulin

High-yield: If serum K⁺ is < 3.3 mEq/L, insulin must be WITHHELD until potassium is repleted, because insulin drives K⁺ intracellularly and can trigger fatal cardiac arrhythmia / respiratory muscle paralysis. This "replace potassium before insulin" rule is a favourite single-best-answer question.

3. Insulin

• Regular (soluble) insulin by continuous IV infusion, 0.1 unit/kg/h, with or without an initial 0.1 unit/kg IV bolus.
• Aim to lower glucose by 50–75 mg/dL/h (≈ 10%/h). If it falls too fast, reduce the rate.
• Do not stop insulin when glucose normalises — the endpoint is closure of the anion gap / resolution of ketosis, not euglycaemia. Maintain insulin and add dextrose to fluids instead.
• In mild–moderate DKA, subcutaneous rapid-acting analogues (lispro/aspart) every 1–2 h are an acceptable alternative to IV infusion.

Resolution criteria (all three): glucose < 200 mg/dL AND two of: serum HCO₃⁻ ≥ 15, venous pH > 7.3, anion gap ≤ 12.

4. Bicarbonate (restricted)

High-yield: Bicarbonate is NOT routinely recommended. Reserve it for severe acidosis with pH < 6.9. Indiscriminate use causes paradoxical CNS acidosis, hypokalaemia, delayed ketone clearance, and a leftward shift of the oxygen dissociation curve.

5. Phosphate

Routine phosphate replacement does not improve outcomes and risks hypocalcaemia. Replace only if PO₄³⁻ < 1.0 mg/dL or there is cardiac dysfunction, respiratory depression, or symptomatic anaemia (use potassium phosphate).

6. Transition to subcutaneous insulin

When DKA has resolved and the patient is eating, switch to a basal-bolus SC regimen. Overlap the IV infusion with the first SC dose by 1–2 hours to prevent rebound ketosis (the SC insulin must be "on board" before the infusion is stopped).

Complications

• Hypokalaemia — the commonest iatrogenic and most dangerous complication of treatment.
• Hypoglycaemia — from over-aggressive insulin without timely dextrose.
• Cerebral oedema — the most feared complication, especially in children; mortality is high. Presents with headache, deteriorating consciousness, bradycardia, hypertension hours into treatment. Linked to overly rapid correction of glucose/osmolality and excessive fluids. Treat with mannitol or hypertonic saline.
• Acute kidney injury (prerenal).
• Hyperchloraemic non-anion-gap metabolic acidosis during recovery — from large-volume saline; self-limiting.
• ARDS, venous thromboembolism, aspiration, rhabdomyolysis.
• Mucormycosis (rhino-orbito-cerebral) — classic opportunistic fungal infection in DKA; Rhizopus thrives in the acidotic, hyperglycaemic, iron-rich environment.

High-yield: Cerebral oedema is the leading cause of DKA death in children. Suspect when consciousness deteriorates after initial improvement. Risk factors: severe acidosis, high urea, bicarbonate use, rapid fall in osmolality. First-line treatment is IV mannitol (0.5–1 g/kg).

DKA vs HHS — the key differential

HHS (hyperosmolar hyperglycaemic state) occurs in type 2 diabetes / elderly with enough residual insulin to suppress ketogenesis but not hyperglycaemia, leading to extreme dehydration and hyperosmolality without significant acidosis.

Feature	DKA	HHS
Typical patient	Young, type 1	Elderly, type 2
Onset	Hours–1 day (rapid)	Days–weeks (insidious)
Glucose	> 250 (often 250–600)	> 600 (often > 1000)
Arterial pH	< 7.30	> 7.30 (≥ 7.3)
Serum HCO₃⁻	< 18	> 18 (> 15)
Ketones	Strongly positive	Absent / trace
Anion gap	High (> 12)	Normal / mildly raised
Effective osmolality	Variable, < 320	> 320 mOsm/kg
Mental status	Alert → coma	Profound obtundation/coma more common
Fluid deficit	~5–7 L	~9–10 L (greater)
Mortality	Lower (~1–5%)	Higher (~10–20%)

High-yield: The discriminators tested most: HHS has glucose > 600, osmolality > 320, pH > 7.3, and minimal/no ketones; DKA has glucose > 250, pH < 7.3, HCO₃⁻ < 18, and prominent ketones. Overlap ("mixed DKA-HHS") exists in up to a third of cases.

Other differentials to consider

• Other causes of HAGMA — mnemonic "GOLD MARK": Glycols (ethylene/propylene), Oxoproline, Lactic acidosis, D-lactic acidosis, Methanol, Aspirin (salicylates), Renal failure, Ketoacidosis (diabetic, alcoholic, starvation).
• Alcoholic ketoacidosis — recent binge, low/normal glucose, β-OHB predominant; responds to dextrose + thiamine.
• Starvation ketosis — mild, HCO₃⁻ rarely < 18.
• Lactic acidosis, sepsis, salicylate poisoning — overlap with high anion gap.

Recently asked / exam angle

• "Replace potassium before insulin when K⁺ < 3.3" — repeatedly asked sequencing question; classic single-best-answer trap.
• Euglycaemic DKA with SGLT2 inhibitors — a modern favourite; normal glucose does not exclude DKA.
• Investigation of choice / best marker of resolution = β-hydroxybutyrate, and why the nitroprusside (urine ketone) test underestimates early DKA.
• First step in management = IV fluids (normal saline), not insulin.
• Bicarbonate only if pH < 6.9; dextrose added when glucose ~200.
• Cerebral oedema in a child improving then deteriorating — recognise and treat with mannitol.
• Effective osmolality formula (excludes urea) and corrected sodium calculations.
• DKA vs HHS table values — glucose, pH, osmolality, ketones — pure recall MCQs.
• Mucormycosis as an associated infection in poorly controlled DKA.

Rapid revision

1. DKA triad: hyperglycaemia (> 250) + ketonaemia + HAGMA (pH < 7.3, HCO₃⁻ < 18, anion gap > 12).
2. Commonest precipitant overall = infection; commonest in young type 1 = insulin omission.
3. SGLT2 inhibitors → euglycaemic DKA (also pregnancy, alcohol, starvation).
4. Core defect = high glucagon-to-insulin ratio → lipolysis → ketone bodies.
5. β-hydroxybutyrate is the predominant ketone and the best marker; urine nitroprusside test misses it.
6. First treatment step = IV 0.9% normal saline, NOT insulin.
7. Hold insulin if K⁺ < 3.3 — replace potassium first.
8. Insulin infusion 0.1 U/kg/h; lower glucose by 50–75 mg/dL/h; endpoint = anion gap closure, not euglycaemia.
9. Add 5% dextrose when glucose ≈ 200 mg/dL; overlap IV and SC insulin by 1–2 h on transition.
10. Bicarbonate only if pH < 6.9; phosphate only if < 1.0 mg/dL.
11. Most feared complication = cerebral oedema (children) → treat with mannitol; commonest iatrogenic = hypokalaemia.
12. HHS: glucose > 600, osmolality > 320, pH > 7.3, no ketones, elderly type 2, higher mortality; mucormycosis is the classic opportunistic infection in DKA.