5 Signs Your Blood Sugar Is Too High and When to Get Help

Short answer: Five common signs of high blood sugar are needing to pee a lot (often at night), feeling very thirsty, blurry vision, feeling very tired, and sores that heal slowly or more infections than usual. These signs can have other causes, and many people with type 2 diabetes have no symptoms at all. If you notice any of these, get your blood sugar tested. If you have vomiting you can't stop, fruity-smelling breath, shortness of breath, or confusion, get urgent help instead of waiting for an appointment.

The 5 Signs Your Blood Sugar May Be Too High

The National Heart, Lung, and Blood Institute (NHLBI) lists these among the symptoms that should prompt a blood sugar test right away.

Peeing a lot, often at night. Needing the bathroom far more than usual is one of the most common early signs.
Feeling very thirsty. Thirst that doesn't match what you've been drinking is worth noting.
Blurry vision. NHLBI lists blurred vision as both an early symptom of high blood sugar and a general diabetes symptom.
Feeling very tired. NHLBI describes feeling more tired than usual as an early symptom.
Sores that heal slowly, or more infections than usual. NHLBI lists both.

NHLBI's full list also includes losing weight without trying, feeling very hungry, numbness or tingling in the hands or feet, and dry skin. Mayo Clinic's list of early signs is similar: frequent urination, increased thirst, blurred vision, and feeling weak or unusually tired.

Why You Might Not Notice Anything

Mayo Clinic notes that high blood sugar usually doesn't cause symptoms until levels are above roughly 180 to 200 mg/dL, and that symptoms develop slowly over days or weeks. It also notes that some people who have had type 2 diabetes for a long time may have no symptoms despite high blood sugar. NHLBI makes the same point: people with type 2 diabetes often have no symptoms, which is why knowing your risk factors and getting tested matters. Not having symptoms doesn't mean your blood sugar is fine.

Why a Heart-Focused Site Is Writing About Blood Sugar

NHLBI states that having diabetes makes heart disease, heart attack, and stroke more likely, and that over time high blood sugar damages blood vessels and nerves, including the nerves that control the heart. Mayo Clinic likewise lists cardiovascular disease among the long-term complications of high blood sugar that isn't treated. Catching high blood sugar early helps protect your heart.

Your Symptom Log: Early Signs vs. Urgent Warning Signs

Copy this into a notes app or print it. Fill in a new entry any day you notice something. Bring it to your appointment. It gives your provider real information to work with.

Column 1: Common Early Signs

Date: ______ Time: ______
Peeing more than usual or waking at night to pee: yes/no
Very thirsty: yes/no
Blurry vision: yes/no
Unusually tired or weak: yes/no
Sore or cut that is slow to heal, or a new infection: yes/no
Other (weight loss without trying, very hungry, tingling in hands or feet, dry skin): ______
Glucose reading, if you have a meter, and when you took it (before eating, after eating): ______
Medications and doses taken today (including any missed): ______

Column 2: Urgent Warning Signs

Date: ______ Time: ______
Vomiting or nausea that won't stop, or can't keep food or fluids down: yes/no
Fruity-smelling breath: yes/no
Shortness of breath: yes/no
Stomach pain: yes/no
Confusion, extreme weakness, or trouble staying awake: yes/no
Glucose reading, if you have a meter: ______
Medications and doses taken today: ______
Who I called and what they told me: ______

Call Today vs. Go Now

Call your provider today if:

You notice one or more of the five signs above and haven't been tested. NHLBI says to get your blood sugar tested right away if you have these symptoms.
You already have diabetes, and your readings are above your target, or you're having symptoms. NHLBI advises talking with your provider about what to do, since you may need to change your medication or what you eat.
You have diabetes and notice a cut, blister, or sign of infection on your feet. NHLBI says people with diabetes need to see a provider for these.

Get urgent help now (urgent care, emergency room, or 911) if:

You have ongoing vomiting or diarrhea and can't keep any food or fluids down. Mayo Clinic lists this as a reason to seek immediate help or call 911.
Your blood sugar stays above 240 mg/dL, and you have symptoms of ketones in your urine. Mayo Clinic lists this as a reason to seek immediate help or call 911.
You have fruity-smelling breath, dry mouth, abdominal pain, nausea and vomiting, shortness of breath, or confusion. Mayo Clinic lists these as symptoms of ketoacidosis, a serious condition that can lead to diabetic coma if untreated, and NHLBI lists them as later symptoms of high blood sugar. We can't diagnose you, so if you're unsure which group you're in, treat it as urgent.
Someone with high blood sugar loses consciousness or can't be woken.

What Counts as “High”?

NHLBI describes high blood sugar (hyperglycemia) as usually 180 mg/dL or above. For diagnosis, NHLBI gives these fasting plasma glucose ranges: 99 mg/dL or below is normal, 100 to 125 is prediabetes, and 126 or higher is diabetes. A non-fasting (random) result below 200 mg/dL is considered normal. Only a health care provider can diagnose diabetes, and your own target range may differ, so ask what yours should be.

Limits of This Article

This is general education, not a diagnosis or personal medical advice.
The five signs above are common but not complete, and they overlap with many other conditions.
Low blood sugar (hypoglycemia) is a different problem with different symptoms, and it needs its own plan from your provider.
Children may not recognize or describe symptoms. Mayo Clinic notes that parents may need to test a child's blood sugar when they suspect it is high.
Pregnancy, type 1 diabetes, and certain medications change the picture. Talk to your provider.

What to Do Next

Start the symptom log above today.
Ask your provider about a blood sugar test, especially if you have risk factors. NHLBI lists these as prediabetes: age 45 or older, extra weight (especially around the waist), little physical activity, a parent or sibling with diabetes, high blood pressure, and others.
If you have diabetes, ask your provider: What are my target numbers? What should I do when my readings are high? When should I call you, and when should I go to the emergency room?
Know the urgent signs above, and make sure the people you live with know them too.

If you're also researching over-the-counter products marketed for blood sugar, this site has a separate page about one of them: Glucozen Drops review. A product page can't tell you why your blood sugar is high or replace testing, and nothing in this article depends on buying anything.

Sources

Source checks completed October 3, 2026.

National Heart, Lung, and Blood Institute. With Every Heartbeat Is Life: A Community Health Worker's Manual on Heart Disease for African Americans, Session 7, “Protect Your Heart From Diabetes.” NHLBI Session 7 (PDF)
National Heart, Lung, and Blood Institute. Your Heart, Your Life: A Promotores de Salud Manual on Heart Disease for Hispanics/Latinos, Session 7, “Protect Your Heart From Diabetes.” NHLBI Session 7 (PDF)
Mayo Clinic. “Hyperglycemia in diabetes: Symptoms and causes.” mayoclinic.org