What to Do if Your Blood Sugar Is Over 400

Blood sugar over 400 mg/dL could mean you're at risk of the potentially fatal diabetic ketoacidosis.
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If you have diabetes, it's very important to keep your blood sugar, or glucose, levels within a healthy range.

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Here's why: If your glucose levels dip too low, you can experience symptoms of hypoglycemia, which include shakiness, a rapid heartbeat and lightheadedness. And, if your blood sugar levels swing too high (called hyperglycemia), you could experience not just long-term health complications, but short-term problems like diabetic ketoacidosis (DKA), a serious condition that could possibly be fatal.


Find out what happens when your blood sugar levels are too high, as well as potential outcomes when they rise above 400 milligrams per deciliter (mg/dL).

What Are the Symptoms of High Blood Sugar?

In general, the American Diabetes Association (ADA) recommends shooting for a blood sugar level of 80 to 130 mg/dL before a meal and a level of less than 180 mg/dL after a meal. Still, because people's target blood glucose levels can vary, it's best to work with your doctor or health care provider to determine the right numbers for you.


Read more:What Are Normal Blood Sugar Levels and What Happens If They're High?

If your blood sugar levels are too high, you can experience symptoms like frequent urination and increased thirst. Left untreated, hyperglycemia can develop into diabetic ketoacidosis, which occurs when your body is no longer able to use insulin to break down glucose for energy.

Without insulin, your body begins to break down fats, triggering the production of chemicals called ketones, according to the ADA. Your body can't harbor too many ketones, so it tries to flush them out of the body through the urine — but because the body can't always eliminate them all, they can continue to build up, causing diabetic ketoacidosis.


How Do I Know if I'm at Risk?

Testing your urine with a urine test strip will reveal the presence of ketones in your urine — high levels of these chemicals are a potential signal of diabetic ketoacidosis. Your doctor will tell you when you should perform the test, but the ADA says that, in general, you may want to check your urine for ketones when your blood sugar levels hit more than 240 mg/dL.

Other symptoms of diabetic ketoacidosis include nausea, difficulty breathing, an altered mental state and a fruity odor on the breath.


"In our clinic, if a person has blood sugar levels of over 300 mg/dL, we will check for urine ketones," says Susan Spratt, MD, an endocrinologist and associate professor of medicine at Duke University School of Medicine. "If their blood sugar levels are over 300 mg/dL — and certainly over 400 mg/dL — we're concerned that they may be going into diabetic ketoacidosis."

If your urine test reveals that ketones are present, call your doctor, who can give you further instructions. You may need to go to the emergency room to seek treatment right away. The ADA says that if you have ketones present in the body, you shouldn't exercise. In this case, exercise can cause your blood sugar levels to spike even higher.

If your blood sugar levels are over 400 mg/dL, you could also be at risk for dehydration, says Dr. Spratt. During treatment, your doctors will give you insulin to stabilize your blood sugar levels and replace any fluids you might have lost through urination or vomiting, according to the U.S. National Library of Medicine.

Read more:What Is a Healthy Blood Sugar Reading in the Morning?

Diabetes Numbers Warnings and Precautions

If your blood sugar reading is over 400 mg/dL, there is a chance that you have a false reading — particularly if you aren't experiencing any symptoms. For example, if there were food particles on your fingers or you used outdated or improperly stored test strips, you might have gotten an inaccurate reading.

If you re-test your levels and your blood sugar is indeed above 400 mg/dL, follow the advice your doctor has given you — whether that includes taking extra insulin or drinking more water — and contact him or her for further treatment advice.

If you have symptoms of diabetic ketoacidosis, you may need to seek immediate medical attention. Without treatment, diabetic ketoacidosis can lead to a diabetic coma and death. Diabetes statistics show the condition was the seventh leading cause of death in the U.S. in 2017, according to the ADA, so it's important to receive the right medical care right away.

Read more:177 Type 1 Diabetes Statistics You Should Know


Is This an Emergency?

If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911. If you think you may have COVID-19, use the CDC’s Coronavirus Self-Checker.
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