Diabetes on the NCLEX: DKA vs HHS and Low vs High Blood Sugar

Diabetes questions come down to two clean splits. First, is the blood sugar too low or too high? A low crashes in minutes and leaves the client cold, clammy, shaky, and confused, while a high builds over hours with thirst, frequent urination, and warm, dry skin. Second, when a high becomes an emergency, is it DKA (ketones and acid, usually in type 1) or HHS (an enormous sugar and severe dehydration without much acid, usually in type 2)? Get those two splits down and the first nursing action for each, and this whole topic turns into fast points.

Low or high? Onset is your first clue

Before you memorize a single sign, anchor on timing. Hypoglycemia comes on fast, over minutes, because the brain notices a fuel shortage almost immediately and the body dumps adrenaline to fight it. Hyperglycemia comes on slowly, over hours to days, as sugar climbs and slowly pulls water out of the body. So a client who was fine an hour ago and is now sweaty and shaky is almost certainly low, while one who has been thirsty and urinating all day is high.

Two rhymes carry the skin findings the exam loves. Cold and clammy, need some candy is a low: pale, sweaty, cool skin from the adrenaline surge. Hot and dry, sugar high is a high: warm, flushed, dry skin from dehydration. Practice sorting the signs below, then read on for how you actually treat each one.

The two blood-sugar pictures side by side

Both extremes are dangerous, but they look and feel different. Hypoglycemia (a low, generally a glucose at or below 70 mg/dL) is an emergency of the moment because the brain is starving right now. Hyperglycemia (a high) does its damage more slowly by dehydrating the body and, in a full crisis, tipping the blood acidic. Keep this table as your quick reference.

Treating a low: the Rule of 15

A low is the one you treat immediately, before you finish charting or call anyone, because the brain has no fuel reserve. If the client is awake and can swallow safely, use the Rule of 15.

1. Give 15 grams of fast-acting carbohydrate: about 4 ounces (half a cup) of juice or regular soda, 3 to 4 glucose tablets per the label, or a tablespoon of honey or sugar.
2. Wait 15 minutes, then recheck the blood glucose.
3. If it is still at or below 70 mg/dL, give another 15 grams and recheck again in 15 minutes.
4. Once it is back above 70, follow with a protein-and-carbohydrate snack (like crackers with cheese) if the next meal is not soon, so the sugar does not drop again.

The exam loves the unconscious twist. If the client cannot swallow safely (drowsy, seizing, or unresponsive), do not put food or fluid in the mouth, because it will go into the lungs. Give glucagon by intramuscular or subcutaneous injection, or IV dextrose in a hospital setting, and turn the client on their side since glucagon often causes vomiting.

The two hyperglycemic emergencies: DKA vs HHS

When a high spirals into a crisis, it lands in one of two buckets. Diabetic ketoacidosis (DKA) happens when there is so little insulin that cells cannot use sugar at all, so the body burns fat and floods the blood with acidic ketones. It is most common in type 1 diabetes and comes on fast, often within a day. Hyperglycemic hyperosmolar state (HHS) happens when there is just enough insulin to hold off ketones but not enough to control the sugar, so glucose climbs enormously high and dehydration becomes profound. It is most common in type 2 diabetes, often in older adults, and builds over days to weeks. Both link tightly to the endocrine and fluid and electrolyte content you are already studying.

The nursing priorities in DKA and HHS

Here is where students lose points by reaching for insulin first. In both DKA and HHS the client is severely dehydrated, so the opening priority is volume, not sugar.

1. Fluids first. Start IV 0.9% normal saline (an isotonic fluid) to refill the tank. See the IV fluids guide for why isotonic saline is the resuscitation choice.
2. Then insulin. Regular insulin by IV infusion is started about an hour into fluids, and it is titrated so the glucose falls in a controlled, steady way rather than crashing.
3. Watch the potassium the whole time. This is the classic tested trap, covered next.
4. Add dextrose when glucose reaches roughly 200 to 250 mg/dL so the insulin can keep clearing ketones (in DKA) without dropping the client into a low.

The potassium story is the single most tested detail here. Acidosis and the lack of insulin push potassium out of the cells and into the blood, so the first serum potassium can read normal or even high, even though total body potassium is badly depleted. The moment you start insulin, potassium rushes back into the cells, and the serum level can plummet into dangerous hypokalemia. That is why potassium is monitored closely and replaced early.

The Kussmaul breathing of DKA is the lungs trying to blow off acid, which connects straight to your acid-base and ABG work: DKA is a metabolic acidosis, and the fast, deep breathing is respiratory compensation. Timing insulin correctly also ties back to the insulin onset, peak, and duration chart, since regular insulin is the one used IV in a crisis.

• Onset sorts low from high. A low crashes in minutes with cold, clammy, shaky, confused; a high builds over hours with the three Ps and warm, dry skin.
• Rule of 15 for a conscious low. 15 g fast carbohydrate, recheck in 15 minutes, repeat if still at or below 70. If the client cannot swallow, give glucagon, never oral food.
• DKA has ketones and acid; HHS has the huge sugar. DKA (usually type 1): fruity breath, Kussmaul breathing, pH under 7.3. HHS (usually type 2): glucose over 600, osmolality over 320, minimal ketones.
• Fluids first, then insulin, in both crises. Start 0.9% normal saline before insulin, because both clients are severely dehydrated.
• Potassium is the tested trap. Serum potassium can look normal while total body stores are depleted; insulin drops it fast. Hold insulin if potassium is under 3.3 mEq/L.