Your next patient is a 24-year-old man who has been very thirsty and getting breathless over the last 2 days. Here's how the diabetic ketoacidosis case unfolds and what to pick up on the way.

This diabetic ketoacidosis case can be missed because two days of thirst, vomiting and breathlessness can sound like a mild viral illness or simple dehydration. Deep sighing heavy breathing may be mistaken for a primary respiratory problem, drowsiness after a sore throat can be written off as post viral fatigue, and a sweet fruity breath is easy to overlook in a rushed clerking.

This page walks through how the case presents, what to pick up in the history, the tests and the teaching points, sticking to the facts in front of you: extreme thirst with heavy urine output, repeated vomiting with poor fluid intake, deep breathing with breathlessness, marked drowsiness, a recent flu-like illness and the pear drop smell on the breath.

How the case presents

Your next patient is a 24-year-old man who has been very thirsty and getting breathless over the last 2 days. In their own words: "Very thirsty and breathless over the last day or two."

Observations on arrival:

Observation	On arrival
Heart rate	118 beats per minute
Blood pressure	104/64 mmHg
Respiratory rate	30 breaths per minute
Oxygen saturation	98%
Temperature	37.4 °C

What to pick up in the history

These are the findings the case is built around. Each one moves you towards or away from diabetic ketoacidosis, and the scorecard checks whether you found it.

Two days of extreme thirst and heavy urine output: osmotic diuresis from hyperglycaemia anchors the presentation in decompensated diabetes rather than gastroenteritis.
Repeated vomiting, unable to keep fluids down.
Deep sighing heavy breathing with breathlessness: kussmaul respiration signals metabolic acidosis and separates ketoacidosis from simple hyperglycaemia.
Very drowsy and struggling to stay awake: reduced conscious level marks severe ketoacidosis and mandates critical care review and airway protection.
Sore throat and flu-like illness a few days ago.
Sweet, fruity pear-drop smell on his breath: exhaled acetone is a near-specific bedside indicator of ketosis.

Red flags you must not miss

The case marks these as must-elicit. They only come out if you ask.

Very drowsy and struggling to stay awake.
He has had no chest pain or palpitations, and no high fever with shaking chills.

Investigations and what they showed

Venous blood gas: 10, bicarbonate 8 mmol/L, with a raised anion gap; mildly raised lactate. Why it helps: one of the three diagnostic pillars of DKA (acidosis) and the fastest way to confirm it; the pH/bicarbonate also grade severity and are trended to monitor resolution.
Bicarbonate: Low (8 mmol/L, <15). Why it helps: A bicarbonate <15 mmol/L is part of the DKA definition and reflects the severity of the acidosis.
Urea and electrolytes: 8 mmol/L (high initially), sodium low (pseudohyponatraemia), urea and creatinine raised (dehydration/AKI).
Capillary blood glucose: High, 32 mmol/L (well above 11).
Capillary blood ketones: 6 mmol/L (>3). Why it helps: the bedside ketone level is the third diagnostic pillar (ketosis) and is trended (aiming for a fall) to confirm the DKA is resolving.
12-lead ECG: Sinus tachycardia with tall, tented ('peaked') T waves, hyperkalaemic changes; no acute ischaemia.
Urine dipstick / urinalysis: Heavy ketones and glucose; no nitrites/leucocytes. Why it helps: A quick bedside confirmation of ketonuria and glycosuria that also screens the urine for a precipitating infection.
Inspect the tongue: The tongue is dry and heavily furred, with a thick pale coating and no pooled saliva, he has to peel his lips apart to put it out.
Inspect the throat and oropharynx: The oropharynx is diffusely red and injected with prominent vessels over the posterior wall and pillars, but no tonsillar exudate. Why it helps: always hunt for the precipitant.
Inspect the work of breathing: He is breathing deeply and laboriously at about 30 breaths a minute, slow, very deep, sighing respirations with a long inspiration and full expiration (Kussmaul breathing), using his accessory muscles but not gasping or wheezing. His breath smells sweet, of pear drops. Why it helps: kussmaul respiration is the lungs blowing off carbon dioxide to compensate for a severe metabolic acidosis.
Inspect the patient's hydration and nutritional state: He is profoundly dehydrated, dry cracked lips, dry furred tongue, no sweat or saliva, sunken eyes, cool peripheries and a thready tachycardia at 118 with a soft blood pressure of 104/64. He also looks as though he has lost weight recently.
Inspect the eyes: The eyes look sunken into the orbits with dark hollowed lids, and the conjunctivae are dry and lustreless rather than glistening.
Inspect the patient's level of alertness and demeanour: He is drowsy but rousable (GCS around 14), keeps his eyes closed between questions, answers in short exhausted sentences and lets his partner fill in the story.
Inspect the skin: The skin is dry and inelastic, a pinched fold over the forearm or sternum stays tented for several seconds (reduced turgor), and the peripheries are cool with sluggish capillary refill.

Imaging findings

X-ray chest: Clear lung fields, no consolidation. Normal.
CT head: No haemorrhage, mass or oedema. Normal.

Why the diagnosis is diabetic ketoacidosis

Distinguish it from a hyperosmolar hyperglycaemic state (older type 2 diabetics, very high glucose/osmolality but minimal ketosis/acidosis) and from other causes of a high-anion-gap acidosis (lactic acidosis, salicylate poisoning, alcoholic/starvation ketosis).

Diabetic ketoacidosis at a glance

What it is

The result is the triad of hyperglycaemia, ketosis and metabolic acidosis.

Pathogenesis

The body compensates by breaking down fat into free fatty acids, which the liver converts into ketone bodies for an alternative fuel. Ketones are acidic, and as they accumulate faster than the body can buffer them, a metabolic acidosis develops. The lungs try to compensate by blowing off carbon dioxide through deep, rapid Kussmaul breathing, and glucose spilling into the urine drags water with it, causing severe dehydration.

Who it affects

It can occur at any age but is particularly common in children, teenagers and young adults with type 1 diabetes.

How serious it is

DKA is a medical emergency: untreated, it progresses to severe dehydration, life-threatening electrolyte disturbance, coma and death.

Investigations and lab tests

3 or bicarbonate under 15). Hourly capillary glucose and ketones are monitored alongside regular venous gases and potassium. An ECG is useful since both very high and, later, very low potassium can produce dangerous arrhythmias.

At a glance: 3 or bicarbonate <15. Monitor hourly: capillary glucose and ketones. Monitor regularly: venous gas, potassium, ECG.

Teaching points

3 or bicarbonate <15).
5 mmol/L and urine is flowing.
Monitor hourly capillary glucose and ketones with regular venous gases and potassium; the target is clearing the ketones/closing the acidosis, not just lowering the glucose.
DKA causes abdominal pain and a mildly raised amylase and white cell count, do not over-diagnose pancreatitis or infection on these alone.

Practise a similar case

Reading a case is one thing. Asking the right questions when a 24-year-old is sighing with deep, heavy breaths and that pear-drop smell is in the air is another, especially with the clock ticking. Try a fresh simulated patient in acute medicine and see what you spot when the diagnosis is not revealed.

Here's one from the same specialty, with the diagnosis left for you to find. Your next patient is 28 and developed swelling and wheeze 15 minutes after eating. Take this patient's history in Diagnosica. It's free to start, no card needed.

Diabetic ketoacidosis case presentation: history, findings and tests