Can Hyperglycemia Cause Dizziness?
Yes, a blood sugar of 300 mg/dL can absolutely cause dizziness, and you should check for ketones immediately and seek medical attention if you have nausea, vomiting, or feel unwell, as this could indicate diabetic ketoacidosis (DKA), a life-threatening emergency. 1
Why High Blood Sugar Causes Dizziness
Hyperglycemia at 300 mg/dL causes dizziness through several mechanisms:
Osmotic fluid shifts and dehydration: When blood glucose exceeds the renal threshold (typically 180 mg/dL), glucose spills into urine causing excessive urination (polyuria) and subsequent dehydration, which directly causes dizziness and light-headedness 2, 3
Neurological symptoms: Dizziness, blurred vision, and light-headedness form a distinct "neurological" symptom cluster that people with insulin-treated diabetes commonly experience during hyperglycemia 3
Metabolic stress: Severe hyperglycemia can progress to serious metabolic decompensation affecting multiple organ systems 4
Immediate Actions You Should Take
Check for ketones right now - either in your urine or blood if you have a ketone meter. The presence of ketones with hyperglycemia and dizziness may signal impending or established DKA 1, 2
Seek emergency care immediately if you have:
- Nausea or vomiting (these are hallmark DKA symptoms) 1
- Abdominal pain 1
- Confusion or altered mental status 5
- Rapid breathing or shortness of breath 1
If you feel relatively well otherwise:
- Drink water to combat dehydration 4
- Check your blood sugar again in 1-2 hours
- Contact your diabetes care team today to adjust your medications 1
Understanding the Severity
A blood glucose of 300 mg/dL represents significant hyperglycemia that requires medical attention:
- This level far exceeds the renal threshold, causing substantial fluid losses 2
- Institutions have protocols requiring physician notification for blood glucose >350 mg/dL, and you're approaching that threshold 5
- The median blood glucose threshold at which people report hyperglycemic symptoms is 270 mg/dL (15 mmol/L), so your symptoms at 300 mg/dL are expected 3
Common Pitfalls to Avoid
Don't assume dizziness is "just" high blood sugar - while hyperglycemia commonly causes dizziness, you must rule out DKA, especially if you take SGLT2 inhibitors (like empagliflozin, dapagliflozin, canagliflozin), which significantly increase DKA risk even at lower glucose levels 1
Don't wait to see if symptoms resolve on their own - hyperglycemia with symptoms indicates your diabetes control needs immediate adjustment, and delaying treatment increases your risk of complications 1, 6
Don't rely on symptoms alone - dizziness can occur from both hyperglycemia and hypoglycemia, so always confirm with blood glucose testing 5, 3