Insulin Clinics / Monitoring and safety

High blood sugar and DKA

A single high reading is rarely an emergency. The combination of high glucose and ketones — diabetic ketoacidosis — is. This page covers the difference and what to do about each.

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When to worry about a high reading

"High" depends on context. A reading of 220 mg/dL two hours after a large carb-heavy meal is common; the same reading first thing in the morning is more concerning. Most clinicians and guidelines worry less about isolated highs and more about:

• Glucose persistently above 250 mg/dL for several hours, or rising despite a correction.
• Glucose above 250 with any ketones present, in someone with type 1 diabetes (and increasingly considered in type 2 as well).
• Glucose above 300 with symptoms (intense thirst, frequent urination, blurry vision, fatigue).
• Glucose that is unexpectedly high after a confirmed insulin dose — could mean a pen problem, a site problem, or insulin that has gone bad.

Most isolated highs can be addressed with a correction dose calculated by your care team's plan, more water, and a recheck in 1–2 hours. The exception is in type 1 diabetes or in anyone using a pump, where a high reading deserves a closer look at why — pump infusion sets fail, sites become inflamed, and insulin can be ineffective for hours before it is obvious.

Symptoms of sustained high blood sugar

The classic triad has been recognized for over a century:

• Polyuria — urinating much more than usual, including overnight. The kidneys spill glucose, which pulls water with it.
• Polydipsia — intense thirst from the fluid loss.
• Polyphagia — hunger despite eating, because cells cannot use the glucose.

Other common symptoms when glucose has been elevated for hours to days:

• Blurred vision
• Fatigue, sluggishness, low energy
• Headache
• Dry mouth and dry skin
• Slow-healing cuts and frequent infections (over weeks)
• Unintended weight loss (over days to weeks, especially in undiagnosed type 1 diabetes)

If these are gradually building over a week or more, it usually points to a regimen that needs adjusting. If they are appearing fast, over hours, with vomiting or breathing changes, the situation is more urgent — see DKA below.

What diabetic ketoacidosis is

Diabetic ketoacidosis (DKA) is what happens when the body has too little insulin to use glucose for energy and starts breaking down fat instead. Fat breakdown produces ketones, acidic compounds that accumulate in the blood. As ketones rise, blood becomes more acidic, and the body's chemistry tips into a dangerous state.

DKA mostly occurs in type 1 diabetes — sometimes as the first sign of new-onset disease — but it can occur in type 2 diabetes, especially during severe illness, with certain medications (notably SGLT2 inhibitors, which can cause "euglycemic" DKA where glucose is not as high as expected), in pregnancy, or after extreme physiological stress like surgery.

DKA is a medical emergency. Treatment requires intravenous fluids and insulin in a hospital. Without treatment, it is fatal.

Warning signs of DKA

DKA usually develops over hours, not minutes. The early signs blend into "feeling lousy from a high blood sugar"; the later ones are unmistakable.

Early

• Persistently high blood glucose (often above 250 mg/dL, sometimes lower with SGLT2 inhibitors)
• Strong thirst, dry mouth, frequent urination
• Nausea
• Fatigue, headache, generally feeling unwell
• Mild stomach pain
• Ketones present in urine or blood

Later (urgent)

• Vomiting — especially repeated vomiting, which makes it impossible to keep up with fluids and is a major reason DKA progresses fast at home.
• Severe abdominal pain, often mistaken for stomach flu or appendicitis.
• Fruity-smelling breath — an acetone smell, sometimes compared to nail polish remover.
• Deep, rapid breathing known as Kussmaul breathing — the body trying to blow off acid through the lungs.
• Confusion, drowsiness, or trouble staying awake.
• Loss of consciousness.

Ketone testing

There are two ways to test for ketones at home, both available without prescription:

Urine ketone strips

A small color-changing strip is dipped in fresh urine. Available at any pharmacy under brand names like Ketostix or generic store brands. The test detects acetoacetate, one of the ketones, and is a useful screening tool. Limitations:

• Reads what was in the blood hours ago, not right now — it lags during a developing or improving DKA.
• Cannot detect beta-hydroxybutyrate, the dominant ketone in early DKA.
• You need to be able to produce urine — dehydration makes that hard.

Blood ketone meters

Several blood glucose meters also have ketone strips (Precision Xtra, Keto-Mojo, others). They use a fingerstick the same way and measure beta-hydroxybutyrate directly. Blood ketone testing is more accurate, faster, and is the recommended method for anyone using a pump or with a history of DKA. Strips are more expensive than urine strips but a starter pack lasts most people a long time.

Interpreting ketone results

Urine ketone strips read in trace / small / moderate / large; "moderate" or "large" is the urgent zone, especially with high blood sugar and any nausea or vomiting.

Sick day rules at a high level

Illness raises insulin needs, often dramatically, even when you are eating less. Stress hormones (cortisol, adrenaline) drive glucose up, and infection itself drives it up further. A common mistake — especially in newly diagnosed type 2 diabetes — is to skip insulin because of low food intake. This is one of the fastest paths to DKA.

The general principles, which your care team will tailor to you:

• Never stop your basal insulin, even if you are not eating. Basal covers the liver's glucose release, which keeps going during illness regardless of food.
• Check blood glucose every 2–4 hours while you are sick.
• Test ketones any time blood glucose is over 250, or any time you are vomiting, or any time you feel "off" with diabetes.
• Hydrate aggressively with sugar-free fluids if glucose is high, or sugar-containing fluids if glucose is low or you cannot eat.
• Use small carbs in fluid form if you cannot eat solids — sips of regular soda, juice, broth.
• Add correction doses per your care team's plan. Some plans add 10–20 percent extra rapid-acting insulin during illness.
• Call the care team if you cannot keep fluids down for 4 hours, if ketones are moderate or above, or if blood glucose is over 250 and not coming down with corrections.

The page on sick days, exercise, and pregnancy goes into more detail.

When to go to the ER without delay

• You are vomiting and cannot keep fluids down for more than a few hours.
• Blood ketones are above 1.5 mmol/L and not improving with treatment.
• Urine ketones are "moderate" or "large" with high glucose.
• You have severe abdominal pain, deep rapid breathing, or fruity breath.
• You feel confused or unusually drowsy.
• Your blood sugar is above 600, especially with dry mouth, dizziness, or confusion (this can also signal hyperosmolar hyperglycemic state, more common in older adults with type 2 diabetes).
• You have had no insulin for 24 hours for any reason — supply, pump failure, hospitalization elsewhere — and have type 1 diabetes.
• A pump or sensor failed and you do not have backup long-acting insulin available.

DKA is uncomfortable to treat — IV fluids, frequent labs, sometimes admission for a day or two — but it is treatable. Catching it early is the difference between a few hours in the ER and a stay in intensive care.