Internal Medicine
Symptoms of High Blood Sugar
Reviewed by the JordanMedHub Medical Editorial Team · 9/12/2026
Quick Answer
High blood sugar can develop gradually or suddenly, and the symptoms differ depending on how high it gets and how fast. Here's what to watch for.
In this article
High blood sugar, or hyperglycemia, occurs when there's too much glucose in the bloodstream — most often because of undiagnosed or poorly managed diabetes.
Common Symptoms
- Increased thirst
- Frequent urination
- Fatigue
- Blurred vision
- Headache
- Slow-healing cuts or wounds
These symptoms often develop gradually, especially in type 2 diabetes, which is part of why high blood sugar can go unnoticed for a long time.
Severe Symptoms That Need Urgent Attention
Very high blood sugar, especially in people with type 1 diabetes, can lead to diabetic ketoacidosis (DKA) — a serious complication with symptoms including confusion, rapid breathing, fruity-smelling breath, nausea, and vomiting. A related emergency, hyperosmolar hyperglycemic state (HHS), is more common in type 2 diabetes and can develop more gradually — look out for extreme thirst, very frequent urination, severe dehydration, weakness, and confusion, even without the fruity breath or rapid breathing seen in DKA.
Disclaimer
This guide is for general education only and does not diagnose or recommend treatment for any individual. If you have very high blood sugar along with confusion, rapid breathing, or fruity-smelling breath, seek emergency medical care rather than waiting to see if it improves.
Frequently Asked Questions
What are the early signs of high blood sugar?
Increased thirst, frequent urination, and fatigue are among the earliest and most common signs, though they often develop gradually.
How high does blood sugar have to be to cause symptoms?
This varies by person — some people notice symptoms at moderately elevated levels, while others feel nothing until blood sugar is very high. This is why relying on symptoms alone isn't a substitute for testing.
Written by JordanMedHub Medical Editorial Team
Updated 9/13/2026
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