Diabetic ketoacidosis vs hyperosmolar hyperglycemic state
NCLEX-RN topic: Illness management
- DKA: almost no insulin, so ketones build up and blood turns acidic.
- HHS: some insulin, few ketones, glucose often above 600 mg/dL.
- Fluids first; check potassium before insulin; delay insulin if potassium is below 3.5 mEq/L.
- Potassium falls fast once insulin starts, even if it was high.
- Glucose below 250 mg/dL: add dextrose and keep the insulin running.
Key facts
- DKA: glucose usually above 250 mg/dL, ketones in blood and urine, metabolic acidosis (pH 7.3 or lower), develops within about 24 hours, most often in type 1 diabetes.
- HHS: glucose often above 600 mg/dL, normal pH, little or no ketones, develops over days to weeks, most often in older adults with type 2 diabetes.
- Kussmaul respirations (deep, labored breathing) are the lungs blowing off CO2 to offset ketoacidosis; fruity breath comes from ketones.
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- Infection and missed insulin doses are the most frequent triggers of both crises.
- Treatment order: IV fluids first, then IV insulin, with potassium checked before insulin starts; insulin is delayed if potassium is below 3.5 mEq/L.
- Insulin and correction of acidosis push potassium into cells, so serum potassium falls during treatment even if it was high at first.
- When glucose falls below 250 mg/dL, 5–10% dextrose is added to the IV fluid and insulin continues until the ketoacidosis resolves.
Quick check1 question · 2 more at the end
A client with diabetic ketoacidosis has received 1 L of 0.9% sodium chloride. Current results: glucose 486 mg/dL (fasting 70–99 mg/dL), arterial pH 7.18 (7.35–7.45), potassium 3.1 mEq/L (3.5–5.1 mEq/L). A continuous IV insulin infusion is prescribed. Which action should the nurse take first?
Correct answer: B.
Insulin and correction of acidosis drive potassium into the cells, so serum potassium falls during DKA treatment. When potassium is already below 3.5 mEq/L, insulin is delayed and potassium is replaced first (per protocol or after notifying the provider) to prevent dangerous dysrhythmias and muscle weakness. Safety of the heart comes before lowering glucose.
A Starting insulin now would push the already low potassium even lower and risk life-threatening dysrhythmias.
B Correct: current guidance delays insulin and replaces potassium first when potassium is below 3.5 mEq/L.
C Bicarbonate is not routine in DKA and is considered only when pH is below 7.0; it would also lower potassium.
D Dextrose is added only after glucose falls below about 250 mg/dL; at 486 mg/dL it is not indicated.
Full lesson
Each part starts with its main idea. Open a part when you want the details.
The short answer: Diabetic ketoacidosis (DKA) happens when there is almost no insulin, so the body burns fat, makes ketones and becomes acidotic; it causes Kussmaul breathing and fruity breath. Hyperosmolar hyperglycemic state (HHS) happens with some insulin, so there are few ketones, but glucose climbs extremely high, causing severe dehydration and confusion. Both need IV fluids, IV insulin and close potassium monitoring.
1 What separates DKA from HHS?The difference comes down to whether the pancreas still makes any insulin. 1 min
The difference comes down to whether the pancreas still makes any insulin. That single fact explains almost every other difference.
In diabetic ketoacidosis (DKA), insulin is missing, so glucose cannot enter cells. The body breaks down fat for fuel, the liver makes ketones, and ketones make the blood acidic (metabolic acidosis).
In hyperosmolar hyperglycemic state (HHS), a little insulin is still present. That is enough to block heavy fat breakdown, so ketones stay low, but not enough to control glucose. Glucose climbs extremely high, pulls water out of cells, and the client becomes severely dehydrated and hyperosmolar.
2 How do the two crises compare?DKA is fast and acidotic; HHS is slow and dehydrated. 1 min
DKA is fast and acidotic; HHS is slow and dehydrated. Use this table to sort cues quickly.
| Feature | DKA | HHS |
|---|---|---|
| Usual client | Type 1 diabetes (also type 2 without insulin) | Type 2 diabetes, often older adults |
| Onset | Usually within 24 hours | Days to weeks |
| Blood glucose | Above 250 mg/dL | Often above 600 mg/dL |
| pH (7.35–7.45) | 7.3 or lower | Normal |
| Ketones | Present in blood and urine | Absent or mild |
| Hallmark cues | Kussmaul breathing, fruity breath, abdominal pain, vomiting | Extreme dehydration, high sodium, confusion, seizures, coma |
| Mortality | About 1% | Up to 20% |
Both cause intense thirst, frequent urination and altered mental status. Both are usually triggered by infection or missed insulin doses, so always look for the trigger.
3 Why does the client with DKA breathe so deeply?Kussmaul respirations are the body's attempt to fix the acid problem through the lungs. 1 min
Kussmaul respirations are the body's attempt to fix the acid problem through the lungs. Carbon dioxide forms acid in the blood, so breathing deeply and quickly blows off CO2 and raises the pH a little.
On an arterial blood gas this is metabolic acidosis: pH below 7.35 and bicarbonate below 22 mEq/L, with PaCO2 falling below 35 mm Hg as the lungs compensate. The fruity smell on the breath comes from ketones.
4 Why does potassium need so much attention?Potassium is the lab value most likely to turn dangerous during treatment. 1 min
Potassium is the lab value most likely to turn dangerous during treatment. Most clients with DKA arrive with a normal or even high serum potassium because acidosis and lack of insulin keep potassium outside the cells.
Once treatment begins, insulin, fluids and correction of acidosis move potassium back into cells, and serum potassium can drop quickly. Low potassium can cause dangerous dysrhythmias and muscle weakness. That is why potassium is checked before insulin starts and rechecked often.
5 What the nurse doesThe nurse restores volume first, then insulin, while guarding potassium and glucose. 1 min
The nurse restores volume first, then insulin, while guarding potassium and glucose. Severe DKA and HHS are managed in an intensive care unit.
- Assess: airway, mental status, vital signs, signs of dehydration, breathing pattern, glucose, ketones, ABG, electrolytes, and possible infection.
- Fluids first: infuse isotonic saline or a balanced crystalloid as prescribed. Use smaller volumes and closer monitoring in older adults and clients with heart or kidney failure.
- Check potassium, then insulin: start the prescribed IV insulin infusion only after the potassium result is known. Current adult guidance delays insulin and replaces potassium first if potassium is below 3.5 mEq/L. Potassium is added to fluids once it falls below 5.0 mEq/L.
- Watch glucose: check capillary glucose every 1–2 hours. When it falls below 250 mg/dL, expect 5–10% dextrose added to the IV fluid and a lower insulin rate, so insulin can keep clearing ketones without causing hypoglycemia.
- Transition safely: give subcutaneous basal insulin 1–2 hours before the IV insulin is stopped.
- Teach: on sick days, check glucose at least every 4 hours and keep taking insulin as the provider directs, because missed insulin is a common trigger. Test urine ketones when advised, and seek care for vomiting, fruity breath or trouble breathing.
Common mistakes
The traps students fall into most. Read these before you practice.
Watch out: A normal or high potassium in DKA does not mean the body has enough potassium; it drops fast once insulin starts.
Watch out: Add dextrose when glucose reaches about 250 mg/dL, not stop the insulin; insulin is what clears the ketones.
Watch out: HHS has little or no ketosis, not a smaller version of DKA's acidosis.
Watch out: HHS carries a higher mortality than DKA, not a lower one, despite the normal pH.
Watch out: Kussmaul breathing is compensation for acidosis, not a primary lung problem.
How to remember it
Memory hook: DKA has the Ks: Ketones, Kussmaul breathing and a K-potassium trap during treatment. HHS has the Hs: Huge glucose, Heavy dehydration and Hardly any ketones.
Self-check:
- Explain in one sentence why HHS has few ketones.
- A client with DKA has potassium 5.6 mEq/L before insulin. Predict what happens to that value after 3 hours of insulin.
- Glucose is 230 mg/dL but bicarbonate is still 12 mEq/L. Say what you expect to be added and why insulin continues.