What is a serum ketones test?

A serum ketones test determines the levels of ketones in your blood. Ketones are a byproduct produced when your body uses only fat, instead of glucose, for energy. Ketones aren’t harmful in small amounts.

When ketones accumulate in the blood, the body enters ketosis. For some people, ketosis is normal. Low-carbohydrate diets can induce this state. This is sometimes called nutritional ketosis.

If you have type 1 diabetes, you may be at risk for diabetic ketoacidosis (DKA), which is a life-threatening complication in which your blood becomes too acidic. It can lead to a diabetic coma or death.

Contact your doctor immediately if you have diabetes and have a moderate or high reading for ketones. Some newer blood glucose meters will test blood ketone levels. Otherwise, you can use urine ketone strips to measure your urine ketone level. DKA can develop within 24 hours and can lead to life-threatening conditions if left untreated.

Although it’s rare, people with type 2 diabetes do develop DKA, according to Diabetes Forecast. Some people may also have alcoholic ketoacidosis from long-term alcohol abuse or starvation ketoacidosis from fasting too long.

Call your doctor immediately if your blood sugar levels are high, your ketone levels are moderate or high, or if you’re feeling:

  • pain in the abdomen
  • nauseated or you’re vomiting for over 4 hours
  • sick with a cold or the flu
  • excessive thirst and symptoms of dehydration
  • flushed, especially on your skin
  • shortness of breath, or breathing rapidly

You may also have a fruity or metallic scent on your breath, and a blood sugar level more than 240 milligrams per deciliter (mg/dL). All of these symptoms can be warning symptoms of DKA, especially if you have type 1 diabetes.

The only complications that come from a serum ketone test come from taking a blood sample. The healthcare provider may have difficulty finding a good vein from which to take the blood sample, and you may have a slight prick sensation or bruising at the site of the needle insertion. These symptoms are temporary and will resolve on their own after the test, or within a few days.

Doctors use serum ketone tests primarily for screening DKA, but they may order them to diagnose alcoholic ketoacidosis or starvation as well. Pregnant women with diabetes will often take the urine ketone test if their meters aren’t able to read blood ketone levels to track ketones frequently.

The serum ketone test, also known as the blood ketone test, looks at how much ketone is in your blood at the time. Your doctor can test for the three known ketone bodies separately. They include:

  • acetoacetate
  • beta-hydroxybutyrate
  • acetone

The results aren’t interchangeable. They can help diagnose different conditions.

Beta-hydroxybutyrate indicates DKA and accounts for 75 percent of ketones. High levels of acetone indicate acetone poisoning from alcohol, paints, and nail polish remover.

You should test for ketones if you:

  • have symptoms of ketoacidosis, such as excessive thirst, fatigue, and fruity breath
  • are sick or have an infection
  • have blood sugar levels above 240 mg/dL
  • drink a lot of alcohol and eat minimally

A serum ketone test is done in a laboratory setting using a sample of your blood. Your doctor will tell you if you need to prepare and how to prepare if you do.

A healthcare provider will use a long, thin needle to draw several small vials of blood from your arm. They’ll send the samples to a lab for testing.

After the blood draw, your doctor will place a bandage over the injection site. This can be taken off after an hour. The spot may feel tender or sore afterward, but this typically goes away by the end of the day.

Home monitoring

Home kits for testing ketones in the blood are available. You should use clean, washed hands before drawing blood. When you place your blood on the strip, the monitor will display the results about 20 to 30 seconds later. Otherwise, you can monitor for ketones using urine ketone strips.

When your test results are available, your doctor will review them with you. This may be over the phone or at a follow-up appointment.

Serum ketone readings (mmol/L)What the results mean
1.5 or lessThis value is normal.
1.6 to 3.0Check again in 2-4 hours.
over 3.0Go to the ER immediately.

High levels of ketones in the blood can indicate:

  • DKA
  • starvation
  • uncontrolled serum glucose levels
  • alcoholic ketoacidosis

You can still have ketones even if you don’t have diabetes. The presence of ketones tends to be higher in people:

  • on a low-carbohydrate diet
  • who have an eating disorder or are in treatment for one
  • who are constantly vomiting
  • who are alcoholics

You may want to consider them with your blood sugar level. A normal blood sugar level for someone without diabetes is 70-100 mg/dL before eating and up to 140 mg/dL two hours after.

Drinking more water and sugar-free fluids and not exercising are things you can do immediately if your tests return high. You may also need to call your doctor for more insulin.

Go to the ER immediately if you have moderate or large amounts of ketones in either your blood or urine. This indicates that you have ketoacidosis, and it can lead to a coma or have other life-threatening consequences.