⬆️Hyperglycemia (High Blood Sugar)
Hyperglycemia is blood glucose persistently above your target range. While a single high reading is not an emergency, chronic or severely elevated blood sugar can quickly progress to life-threatening conditions.
What Is Hyperglycemia?
Hyperglycemia means blood glucose is above your target range. Clinical thresholds commonly used:
- Above target: >130 mg/dL (7.2 mmol/L) fasting or >180 mg/dL (10 mmol/L) post-meal (per ADA)
- Significant hyperglycemia: >250 mg/dL (13.9 mmol/L) — check for ketones
- Danger zone: >400 mg/dL (22.2 mmol/L) — seek medical evaluation, especially with symptoms
Chronically high blood glucose damages blood vessels and nerves over time, leading to long-term complications including retinopathy (eye disease), nephropathy (kidney disease), neuropathy (nerve damage), and cardiovascular disease. Acutely severe hyperglycemia can cause Diabetic Ketoacidosis (DKA) or Hyperosmolar Hyperglycemic State (HHS), both of which are life-threatening emergencies.
Common Causes of Hyperglycemia
- Missed or insufficient insulin dose: Forgetting a bolus or taking too little basal insulin
- Dietary excess: Eating more carbohydrates than the bolus covers
- Illness/infection: Stress hormones (cortisol, glucagon) counter insulin and raise blood sugar — even when eating less
- Inactivity: Reduced exercise decreases glucose uptake by muscles
- Insulin delivery failure: Kinked infusion set (pump), lipohypertrophy at injection site, expired insulin, or incorrect insulin concentration
- Medications: Steroids (prednisone), certain antipsychotics, and some diuretics raise blood glucose
- Dawn phenomenon: Hormonal surge in early morning raises fasting blood glucose
Symptoms of Hyperglycemia
| Symptom | Physiological Cause |
|---|---|
| Polyuria (frequent urination) | Kidneys excrete excess glucose, taking water with it (osmotic diuresis) |
| Polydipsia (excessive thirst) | Fluid loss from osmotic diuresis triggers thirst |
| Fatigue/lethargy | Cells can't use glucose for energy without insulin |
| Blurred vision | High glucose causes fluid shifts in the lens of the eye |
| Headache | Dehydration and cerebral effects of osmotic changes |
| Slow wound healing | High glucose impairs immune function and blood vessel integrity |
DKA Warning Signs — Seek Emergency Care
Diabetic Ketoacidosis (DKA) is a life-threatening emergency that occurs when severe insulin deficiency forces the body to break down fat for fuel at an uncontrolled rate, producing acidic ketone bodies. DKA is most common in Type 1 diabetes but can occur in Type 2.
- Nausea, vomiting, or severe abdominal pain
- Sweet, fruity, or acetone-like breath odor
- Rapid, deep breathing (Kussmaul respirations)
- Moderate to large ketones on urine or blood ketone test
- Blood glucose persistently >250 mg/dL despite corrections
- Extreme weakness, confusion, or difficulty staying awake
Checking Ketones
If blood glucose is >250 mg/dL, check for ketones — especially for Type 1 patients. Options:
- Urine ketone strips: Dip in urine for 15 seconds; read result at 40–60 seconds. Results: Negative / Trace / Small / Moderate / Large
- Blood ketone meters: More accurate and faster. Values: <0.6 mmol/L (normal), 0.6–1.5 (borderline), >1.5 (elevated — contact provider), >3.0 (DKA range — emergency)
How to Treat Mild-to-Moderate Hyperglycemia
- Check blood glucose with a meter or CGM to confirm the reading.
- Identify and correct the cause (missed dose, dietary excess, pump occlusion, etc.).
- Calculate a correction dose using your Insulin Sensitivity Factor (ISF): Correction = (Current BG − Target BG) ÷ ISF
- Check your active IOB before correcting. If significant IOB remains from a recent dose, wait for it to act before stacking another correction.
- Hydrate. High blood glucose causes osmotic fluid loss. Drink water to stay hydrated — but avoid sugary drinks.
- Check ketones if BG >250 mg/dL. If ketones are elevated, contact your care team before self-treating with additional insulin.
- Recheck in 2 hours. If BG is not responding, contact your diabetes care team.
Sick-Day Rules
Illness — even minor infections, colds, or GI upset — can dramatically raise blood glucose due to stress hormone release. Key sick-day rules for insulin-using patients:
- Never skip your basal insulin even if you're not eating. Basal insulin is needed to prevent DKA, especially in T1D.
- Check blood glucose every 2–4 hours when ill.
- Check ketones if BG >250 mg/dL.
- Stay hydrated with sugar-free fluids. If unable to keep fluids down, seek emergency care.
- Take correction doses as needed for elevated BG, guided by your ISF.
- Contact your care team if you have vomiting, ketones, cannot eat for more than 4–6 hours, or blood glucose is persistently >300 mg/dL.