Frequent urination. When your blood sugar is high, a common sign is frequent urination. This is related to thirst as well because the thirstier you are, the more you will drink. However, not all frequent urination means high blood sugar. Caffeine and diuretic drugs can cause increased urination too.

Abnormal blood glucose levels. A sign of a high blood sugar level is if your fasting glucose is above 100 mg/dL. You may notice this if you often feel tired after any meal. This is a result of your blood sugar spiking.

Thirst. One common sign of high blood sugar is increased thirst. This does not always mean you have high blood sugar, but it is a sign of elevated glucose levels in your blood.

Blurred vision. When the glucose in your blood increases to a high enough level, your vision is greatly impacted. If your glucose is high and you have blurred vision, make sure to tell your doctor about both and discuss whether they could be related.

Headaches. Persistent headaches are a common sign of high blood sugar. However, they can be a warning sign of other things too. But if you never used to have headaches and all of a sudden do, it could be due to high glucose levels.

Lightheadedness. Another common symptoms of high blood sugar is feeling lightheaded often, and for no apparent reason. Feeling lightheaded can be associated with very high blood sugar levels. If you experience this symptom, it is important to see a doctor as soon as possible because this can cause you to blackout.