What to Do if Your Blood Sugar Is Over 400

A reading this high requires a calm and methodical response to ensure your safety. Follow these immediate steps while you get in touch with your healthcare provider.

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Test Your Blood Sugar Again Contact Your Doctor Immediately Test Your Urine for Ketones Know When to Call 911

Test Your Blood Sugar Again

If you get a reading over 400 mg/dL, recheck your blood sugar to rule out a false reading, especially if you don’t have other symptoms like frequent urination or extreme thirst. An inaccurate result can occur if your hands are not clean, you use expired test strips, or you’ve not kept test strips in the correct storage conditions.

Contact Your Doctor Immediately

If a second test confirms your blood sugar is over 400 mg/dL, call your doctor or endocrinologist right away. Follow the specific treatment plan they have given you for high blood sugar, which may include taking extra insulin or drinking more water, while you wait for their guidance.

Test Your Urine for Ketones

Your doctor may ask you to use a home test strip to check your urine for ketones.

High levels of these chemicals are a potential sign of diabetic ketoacidosis (DKA), a life-threatening complication that happens when your body can’t use insulin and starts breaking down fat for energy instead.

The ADA recommends checking for ketones when your blood sugar level is 240 mg/dL or higher.

“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 professor of medicine at Duke University School of Medicine in Durham, North Carolina.

“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,” says Dr. Spratt.

If ketones are present, your doctor will give you further instructions, which may include going to the emergency room. Do not exercise if you have ketones, as this can make your blood sugar spike even higher.

Know When to Call 911

Untreated hyperglycemia can lead to DKA, which can progress rapidly.

According to the Centers for Disease Control and Prevention, you should seek immediate medical help if you experience DKA symptoms like:

Unusually rapid, deep breathing
A flushed face
Breath that has a distinct fruity smell
Feeling nauseous or vomiting
Abdominal pain
A parched mouth and dry skin
Feeling exhausted
Headache
Muscle aches or stiffness

Even if your symptoms aren’t severe, untreated hyperglycemia can cause long-term complications, including nerve damage (diabetic neuropathy), eye damage (diabetic retinopathy), and kidney or heart problems.

Without immediate treatment, DKA can lead to diabetic coma and death.

Diabetes is the seventh leading cause of death in the United States, so getting medical care right away is critical if you have symptoms of DKA.