What to Do If Your Blood Sugar is Over 400

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).

Warning

If your blood sugar is over 400 (or persistently higher than 240), seek medical attention immediately, according to the Mayo Clinic.

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.

Causes of High Blood Sugar

High blood sugar can come about for a number of reasons. In general, though, if you have diabetes, you can experience high blood sugar episodes because the insulin in your body isn't able to adequately regulate the amount of glucose in your blood, per the Mayo Clinic.

According to the Cleveland Clinic, there are other reasons your blood sugar can spike when you have diabetes, including:

  • You're not taking the right dose of insulin or diabetes medication.
  • The amount of carbohydrates you're eating isn't balanced with your insulin medication dosage.
  • You're less physically active.
  • You're physically or emotionally stressed.
  • You're taking steroid medications.
  • You're experiencing the dawn phenomenon, which is when your body produces a surge of hormones early in the morning.
  • Endocrine conditions like Cushing syndrome
  • Pancreatic diseases like pancreatitis and cystic fibrosis
  • Certain medications like diuretics and steroids
  • Gestational diabetes
  • Side effects from surgery

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.

Warning

Without treatment, diabetic ketoacidosis can lead to a diabetic coma and death, so if you have symptoms, seek immediate medical attention. 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 get medical care right away.

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