Quick answer: in adults, diabetic ketoacidosis (DKA) is diagnosed when all three are present: glucose above 11 mmol/L or known diabetes, blood ketones above 3 mmol/L (or urine ketones 2+ or more), and venous pH below 7.3 or bicarbonate below 15 mmol/L. Treatment starts with 0.9% sodium chloride, then a fixed-rate intravenous insulin infusion at 0.1 units/kg/hr, with potassium added once the level is 5.5 mmol/L or below. When glucose falls below 14 mmol/L, add 10% glucose and consider halving the insulin rate. DKA has resolved when ketones are below 0.6 mmol/L and venous pH is above 7.3.
DKA is a favourite MRCEM topic because the management is protocol-driven and full of numbers. Most questions test the diagnostic criteria, the order of treatment and the potassium rules. This guide follows the Joint British Diabetes Societies (JBDS) adult guideline, revised in 2023. Children and young people under 18 are managed with the BSPED guideline, which uses more cautious fluids.
Why DKA happens
A lack of insulin stops cells using glucose, so the body breaks down fat and produces ketones, which cause a raised anion gap metabolic acidosis. High glucose drives an osmotic diuresis, which leads to severe dehydration and loss of sodium and potassium. Common triggers are infection, missed insulin, a new diagnosis of type 1 diabetes, myocardial infarction and SGLT2 inhibitors.
Diagnostic criteria
All three are needed:
| Component | Threshold |
|---|---|
| Glucose | Above 11 mmol/L, or known diabetes |
| Ketones | Blood ketones above 3 mmol/L, or urine ketones 2+ or more |
| Acidosis | Venous pH below 7.3, or bicarbonate below 15 mmol/L |
A venous gas is enough. Arterial sampling is not needed for the diagnosis.
Step 1: fluids
Fluid comes first, using 0.9% sodium chloride.
- Systolic BP below 90 mmHg: 500 mL over 10 to 15 minutes. Repeat if needed and call for senior help.
- Systolic BP 90 mmHg or above: 1 litre over the first hour.
A typical regimen for a 70 kg adult then continues:
| Bag | Rate |
|---|---|
| 1 litre | Over 1 hour |
| 1 litre with potassium | Over 2 hours |
| 1 litre with potassium | Over 2 hours |
| 1 litre with potassium | Over 4 hours |
| 1 litre with potassium | Over 4 hours |
| 1 litre with potassium | Over 6 hours |
Give fluid more cautiously in patients aged 18 to 25, older people, pregnancy, and heart or kidney failure.
Step 2: potassium
Total body potassium is low even when the blood level is normal or high. Insulin then drives potassium into cells and the level falls quickly.
| Potassium in the first 24 hours | Replacement per litre of fluid |
|---|---|
| Above 5.5 mmol/L | None |
| 3.5 to 5.5 mmol/L | 40 mmol |
| Below 3.5 mmol/L | Senior review, as extra potassium is needed |
Step 3: fixed-rate insulin
- Start a fixed-rate intravenous insulin infusion at 0.1 units/kg/hr, using 50 units of soluble insulin in 50 mL of 0.9% sodium chloride.
- Do not give an insulin bolus.
- Continue the patient’s usual long-acting insulin.
- When glucose falls below 14 mmol/L, add 10% glucose at 125 mL/hr alongside the saline, and consider reducing the insulin rate to 0.05 units/kg/hr.
The aim of insulin is to clear ketones, not to normalise glucose.
Monitoring and targets
Check glucose and ketones hourly. Check venous pH, bicarbonate and potassium at 60 minutes, at 2 hours and then every 2 hours. Aim for:
- Ketones falling by at least 0.5 mmol/L per hour
- Bicarbonate rising by at least 3 mmol/L per hour
- Glucose falling by at least 3 mmol/L per hour
- Potassium kept between 4.0 and 5.5 mmol/L
If these targets are not met, check the lines and pump, then increase the insulin rate.
Who needs HDU or critical care?
- Blood ketones above 6 mmol/L
- Bicarbonate below 5 mmol/L, or pH below 7.0
- Potassium below 3.5 mmol/L on admission
- GCS below 12
- Systolic BP below 90 mmHg, or oxygen saturation below 92% on air
- Pulse over 100 or under 60 beats per minute
- Anion gap above 16
Resolution
DKA has resolved when blood ketones are below 0.6 mmol/L and venous pH is above 7.3. Do not rely on bicarbonate, because large volumes of saline cause a hyperchloraemic acidosis. Switch to subcutaneous insulin when the patient is eating and drinking. Give the subcutaneous dose with a meal and stop the infusion 30 to 60 minutes later.
Euglycaemic DKA
DKA can occur with a normal or only mildly raised glucose. Think of it in patients taking SGLT2 inhibitors such as dapagliflozin or empagliflozin, in pregnancy, and in people who are fasting or have already taken insulin. Check ketones in any unwell patient with diabetes, whatever the glucose. Start 10% glucose early and stop the SGLT2 inhibitor.
Complications
- Hypokalaemia and hyperkalaemia
- Hypoglycaemia
- Cerebral oedema, mainly in children and young adults
- Venous thromboembolism, so prescribe prophylactic low molecular weight heparin
- Fluid overload and pulmonary oedema
Common exam traps
- Starting insulin before fluids: fluid resuscitation comes first.
- Giving an insulin bolus: it is not recommended in adults.
- Using a variable-rate sliding scale: DKA needs a weight-based fixed rate.
- Stopping insulin when glucose normalises: add 10% glucose and continue until ketones clear.
- Being reassured by a normal potassium: replace it once the level is 5.5 mmol/L or below.
- Stopping long-acting insulin: continue it throughout.
- Giving bicarbonate: it is not recommended.
- Ruling out DKA because glucose is normal: remember SGLT2 inhibitors.
Summary
- Diagnosis needs glucose above 11 mmol/L (or known diabetes), ketones above 3 mmol/L and pH below 7.3 or bicarbonate below 15 mmol/L.
- Give 0.9% sodium chloride first: 1 litre over an hour, or 500 mL boluses if systolic BP is below 90 mmHg.
- Fixed-rate insulin at 0.1 units/kg/hr, with no bolus. Continue long-acting insulin.
- Add 40 mmol/L of potassium when the level is 3.5 to 5.5 mmol/L.
- Add 10% glucose at 125 mL/hr when glucose is below 14 mmol/L.
- Resolution: ketones below 0.6 mmol/L and pH above 7.3.
Frequently asked questions
What are the diagnostic criteria for DKA?
Glucose above 11 mmol/L or known diabetes, blood ketones above 3 mmol/L or urine ketones 2+ or more, and venous pH below 7.3 or bicarbonate below 15 mmol/L.
What is the insulin dose in DKA?
A fixed-rate intravenous infusion of 0.1 units/kg/hr, with no bolus. It may be reduced to 0.05 units/kg/hr once glucose is below 14 mmol/L.
When should glucose be added?
When blood glucose falls below 14 mmol/L, start 10% glucose at 125 mL/hr and continue the saline.
When has DKA resolved?
When blood ketones are below 0.6 mmol/L and venous pH is above 7.3.
Next steps
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Clinical content checked against the JBDS guideline on the management of diabetic ketoacidosis in adults (revised March 2023) on 5 October 2026. This article is for exam preparation. In clinical practice, always follow your local DKA protocol.