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DKA vs HHS: how to tell them apart
Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are both high blood sugar emergencies. DKA has ketones and acidosis (pH below 7.3) and is more common in type 1 diabetes; HHS has extreme glucose (600 mg/dL or more), severe dehydration and little or no ketones, and is more common in older adults with type 2. Both are treated with IV fluids first, then insulin, while watching potassium.
Side by side
| DKA | HHS | |
|---|---|---|
| Usual client | Type 1 diabetes (can occur in type 2) | Type 2 diabetes, often older adults |
| Onset | Fast, hours to a day or two | Slow, over days |
| Blood glucose | 200 mg/dL or more, or any level in a person with known diabetes | 600 mg/dL or more |
| Ketones | Present (beta-hydroxybutyrate 3.0 mmol/L or more, or urine ketones 2+ or more) | None or mild (beta-hydroxybutyrate below 3.0 mmol/L) |
| pH and bicarbonate | pH below 7.3 and/or bicarbonate below 18 mEq/L | pH 7.3 or higher and bicarbonate 15 mEq/L or higher |
| Serum osmolality | Variable | Effective osmolality above 300 mOsm/kg (total above 320) |
| Key signs | Kussmaul breathing, fruity breath, nausea, vomiting, abdominal pain | Severe dehydration, confusion, seizures or coma |
Nursing priorities for both
- Fluids first: IV isotonic fluid as ordered to restore volume.
- Check potassium before starting insulin. Insulin moves potassium into the cells, so if potassium is below 3.5 mEq/L, replace it and hold insulin until it is above 3.5.
- Start the IV insulin infusion as ordered and check glucose every hour.
- Add dextrose to the IV fluid when glucose falls to the level in the protocol, so insulin can keep clearing ketones without causing a low.
- Monitor potassium, the cardiac rhythm, neuro status, intake and output.
- Correct glucose and sodium gradually; changes that are too fast raise the risk of cerebral edema.
How to remember it
- DKA: think Ketones and Kussmaul, acid in the blood.
- HHS: think Hyperosmolar, Hugely high sugar, Hydration lost.
NCLEX tip: The NCLEX favorite is potassium: in DKA the first potassium level can look normal or high, but total body potassium is low, and it drops once insulin starts. Check it before and during insulin therapy.
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Frequently asked questions
What is the main difference between DKA and HHS?
DKA produces ketones and acidosis; HHS has much higher glucose and severe dehydration with little or no ketones.
Which is more dangerous, DKA or HHS?
Both are emergencies. HHS has a higher death rate, partly because it often affects older adults with other illnesses.
Why give fluids before insulin?
Both conditions cause major fluid loss. Fluids restore circulation and start lowering glucose, and insulin given into a dry circulation can drop blood pressure further.
What is the hallmark of HHS?
Extremely high blood glucose (600 mg/dL or more) with very high serum osmolality and severe dehydration, but little or no ketones and no significant acidosis. Confusion and other neuro changes are common.
What are the three criteria for DKA?
Under the 2024 consensus: high glucose (200 mg/dL or more, or known diabetes), ketones (beta-hydroxybutyrate 3.0 mmol/L or more, or urine ketones 2+ or more) and acidosis (pH below 7.3 and/or bicarbonate below 18).
Why is blood sugar higher in HHS than DKA?
HHS develops slowly over days, so glucose keeps climbing and fluid is lost before the client seeks care. In DKA, ketones and acidosis cause symptoms such as vomiting and fast breathing early, so clients often come in at lower glucose levels.
Is HHS hypo or hyperglycemia?
Hyperglycemia. HHS (hyperosmolar hyperglycemic state) has extremely high blood glucose, 600 mg/dL or more, with severe dehydration and little or no ketones.
How to distinguish between HHS and DKA?
Look at ketones and pH. DKA has significant ketones and acidosis (pH below 7.3 and/or bicarbonate below 18). HHS has glucose of 600 mg/dL or more, very high osmolality and little or no ketones, with pH 7.3 or higher.
Keep studying
Sources
- Hyperglycemic Crises in Adults With Diabetes: A Consensus Report (Diabetes Care, 2024), ADA, EASD, JBDS, AACE and DTS (open copy on PubMed Central)
- Adult Diabetic Ketoacidosis, StatPearls, NCBI Bookshelf
- Hyperosmolar Hyperglycemic Syndrome, StatPearls, NCBI Bookshelf
For study only, not medical advice. Ranges and protocols vary by facility; follow your program, your facility's policies and the provider's orders.