DKA vs. HHS for NCLEX: Follow Two Patients Beyond the Glucose

One patient arrives vomiting and breathing deeply. Another has become progressively weaker and confused after several days of thirst and frequent urination. Both have high glucose, but the number alone cannot tell you whether the problem is diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS) or an overlapping crisis.

Follow these two fictional adult patients as the laboratory results arrive. The purpose is to compare mechanisms and nursing concerns, not to supply a treatment order set. The current diagnostic framework is the 2024 international consensus report, also reflected in the ADA Standards of Care in Diabetes—2026.

Two arrivals, before the labels

Patient A: A 29-year-old adult with diabetes reports abdominal discomfort and vomiting after an interruption in insulin access. Respirations are deep and rapid; the patient is thirsty and appears dehydrated. The initial glucose is 360 mg/dL.

Patient B: A 74-year-old adult with diabetes has been unwell for several days and unable to keep up with fluid intake. A family member reports increasing confusion. The patient has dry mucous membranes, tachycardia and marked weakness. Glucose is 936 mg/dL.

Both need prompt assessment and escalation through the appropriate clinical pathway. For each, check airway and breathing, circulation, mental status and the immediate clinical condition. Neither the younger age nor the higher glucose assigns a diagnosis by itself. An older adult can have DKA; type 2 diabetes does not exclude it.

The initial symptoms suggest different directions for investigation. Patient A's breathing and gastrointestinal symptoms raise the question of acidosis. Patient B's prolonged fluid loss and cognitive change raise the question of hyperosmolality. Those are working concerns to test, not conclusions to defend before the results return.

Patient A: the ketones explain more than the glucose

The next results are β-hydroxybutyrate 5.2 mmol/L, bicarbonate 12 mmol/L and venous pH 7.25. Sodium is 138 mmol/L. Glucose remains 360 mg/dL.

These findings satisfy the three components of DKA: diabetes or qualifying hyperglycemia, significant ketosis and metabolic acidosis. The glucose is not merely “high enough to be DKA”; ketones and acid–base findings complete the pattern.

Insufficient insulin activity permits fat breakdown and ketone production. Accumulating ketoacids consume bicarbonate. Deep breathing can be a compensatory response to metabolic acidosis, so it should not automatically be attributed to anxiety. The CDC's DKA explanation links inadequate insulin, ketones and the characteristic illness.

The original case values are deliberately coherent: if a blood gas also showed a CO₂ near 28 mmHg, bicarbonate 12 would correspond to an approximate pH of 7.25. For more detailed acid–base interpretation, use the ABG guide; a venous pH used in a DKA assessment is not an arterial oxygenation measurement.

Now make one change: the glucose is below 200 mg/dL, but the patient has a known history of diabetes, significant ketosis and acidosis. DKA still needs consideration. Euglycemic DKA is one reason a memorized rule requiring glucose above 250 mg/dL can fail, particularly in relevant settings such as SGLT2 inhibitor exposure. The complete criteria and clinical assessment matter.

Patient B: make the water loss and osmolality visible

Patient B's additional results are sodium 148 mmol/L, β-hydroxybutyrate 1.1 mmol/L, bicarbonate 24 mmol/L and pH 7.38. The calculated effective serum osmolality is 348 mOsm/kg.

With glucose in mg/dL and sodium in mmol/L, the teaching calculation is 2 × sodium + glucose ÷ 18. Here, 2 × 148 + 936 ÷ 18 = 296 + 52 = 348 mOsm/kg. Using glucose in mmol/L instead removes the division by 18. Mixing those unit systems produces a misleading result.

The pattern supports HHS: severe hyperglycemia and hyperosmolality without significant ketonemia or qualifying acidosis. Glucose-driven osmotic diuresis promotes water and electrolyte losses. Reduced renal clearance and inadequate replacement of water can worsen the cycle. Residual insulin activity may limit substantial ketone production without controlling hyperglycemia.

Confusion is an important assessment finding, not proof that osmolality is its only cause. Infection, medications, stroke and other concurrent conditions may also need evaluation. The Merck professional review of acute diabetes complications discusses the dehydration and neurologic presentation of HHS.

A compact criteria check

For adult DKA, current criteria require all three components: glucose at least 200 mg/dL or prior diabetes; β-hydroxybutyrate at least 3.0 mmol/L or urine ketones at least 2+; and pH below 7.3 and/or bicarbonate below 18 mmol/L.

For adult HHS, all four components are required: glucose at least 600 mg/dL; effective osmolality above 300 mOsm/kg or total osmolality above 320; β-hydroxybutyrate below 3.0 mmol/L or urine ketones below 2+; and pH at least 7.3 with bicarbonate at least 15 mmol/L. Effective and total osmolality are different calculations; the total includes urea.

These thresholds are diagnostic criteria, not normal laboratory ranges, severity scores or automatic nursing orders. Mixed presentations occur. If Patient B instead develops substantial ketonemia and metabolic acidosis, the very high glucose does not make those findings irrelevant.

During treatment, a falling glucose is only part of the story

The team initiates the patient-specific fluid, insulin and electrolyte plan. Nursing surveillance follows perfusion, mental status, vital signs, intake and output, laboratory trends and the response to treatment. Renal or cardiac impairment can change fluid tolerance; the two adults should not receive an assumed identical plan simply because both have a hyperglycemic emergency.

Potassium deserves deliberate attention. A normal or elevated initial serum potassium does not establish that total-body stores are adequate. Insulin and correction of the metabolic disturbance can lower the serum concentration. Review the current result, renal function and ordered replacement and monitoring before administration.

The 2024 consensus identifies low potassium below 3.5 mmol/L as a reason to replace potassium and delay insulin until the concentration rises above 3.5 mmol/L under the treatment protocol. This is a safety condition requiring prompt team communication, not permission to independently choose a replacement dose. Endotext's hyperglycemic crises chapter explains the potassium concern.

Suppose Patient A's glucose improves while ketones remain elevated. Stopping treatment solely because the glucose is lower would ignore the unresolved ketoacidosis. Conversely, a new neurologic change in Patient B during treatment needs immediate reassessment, even if the glucose trend looks better. Resolution depends on the full metabolic and clinical picture.

The laboratory interpretation guide develops this distinction between a changing number and a changing patient. In an ENDPEAK QBank or RN Topics review, explain which finding supports the crisis pattern and which finding changes treatment safety; an AI Tutor discussion is useful only if those two questions stay separate.

Return to the cause before closing the case

Patient A's insulin interruption needs a practical access assessment, not a label of “noncompliance.” Patient B's illness and reduced intake require investigation of the precipitating problem and the support available at home. The 2026 ADA prevention guidance includes attention to barriers that contribute to hyperglycemic crises.

Before naming either emergency on the next question, account for glucose, ketones, acid–base status and osmolality. Then ask what the patient is experiencing now and what could become unsafe during treatment. That explanation is more useful than choosing whichever diagnosis is associated with the largest glucose number.

Adult diagnostic and safety information checked October 2026. Cases and calculations are original ENDPEAK teaching material, not actual patient records. No independent professional diabetes review is claimed. Pediatric and pregnancy management require their own clinical guidance.