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Ketones, blood


At a Glance

Why Get Tested?

To determine the amount of ketones (ketone bodies, acetoacetate, beta-hydroxybutyrate, and acetone) in the blood to help diagnose a life-threatening problem called diabetic ketoacidosis

When to Get Tested?

When you have symptoms associated with ketoacidosis, such as increased urination, excessive thirst, dehydration, rapid breathing, and shortness of breath

Sample Required?

A blood sample drawn from a vein in your arm or from a fingerstick

Test Preparation Needed?

None

The Test Sample

What is being tested?

Ketones or ketone bodies are byproducts of fat metabolism. This test measures the amount of ketones in the blood.

Ketones are produced when glucose is not available to the body's cells as an energy source and/or when the body cannot use glucose as a fuel source because there is no insulin or not enough insulin. Fat is used for fuel instead. When fat is metabolized, byproducts called ketone bodies build up in the blood, causing first ketosis and then progressing to ketoacidosis, a form of metabolic acidosis. This condition is most frequently seen with uncontrolled type 1 diabetes and can be a medical emergency.

There are three ketone bodies – acetoacetate, beta-hydroxybutyrate, and acetone. Acetoacetate is created first. Beta-hydroxybutyrate is created from acetoacetate. Acetone is a spontaneously created side product of acetoacetate. Beta-hydroxybutyrate is the predominant ketone body present in severe diabetic ketoacidosis (DKA). Different ketone tests measure one or more ketone bodies, and their results are not interchangeable.

Blood testing gives a snapshot of the status of ketone accumulation at the time that the sample was collected. Urine ketone testing reflects recent rather than current blood ketones. Urine testing is much more common than blood ketones testing. It may be performed by itself, with a urine glucose test, or as part of a urinalysis. The urine methods measure either acetoacetate or acetoacetate and acetone but do not usually detect beta-hydroxybutyrate.

Blood ketones may be measured in a laboratory or with a handheld monitor. The laboratory test uses serum, the liquid portion of the blood, and typically measures acetoacetate. Beta-hydroxybutyrate can be ordered as a separate blood test.

When whole blood from a fingerstick is tested for ketones using a handheld monitor, the monitor measures beta-hydroxybutyrate. This test may be performed at a person's bedside in a hospital or emergency room, in a doctor's office, or performed by a person at home.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm or by pricking a finger.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Blood ketones are primarily used to screen for, detect, and monitor a serious, sometimes life-threatening condition called diabetic ketoacidosis (DKA) in people with type 1 and sometimes type 2 diabetes. DKA can occur when a diabetic's blood glucose is significantly increased, with illness, severe infection, pregnancy, and a variety of other conditions.

DKA is associated with sudden and severe high blood glucose (acute hyperglycemia), a severe insulin deficiency, and a disruption of the body's acid-base balance. Excess ketones and glucose are dumped into the urine by the kidneys in an effort to flush them from the body. This causes increased urination, thirst, dehydration, and a loss of electrolytes. The affected person may also experience symptoms such as rapid breathing, shortness of breath, a fruity scent to the breath, nausea, vomiting, fatigue, confusion, and eventually coma.

Ketosis and ketoacidosis may also be seen with starvation, alcoholism, and with high-fat, low-carbohydrate diets. It may be induced on purpose in some children with epilepsy who have frequent seizures and do not respond to available medications or other treatments.

There are three ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Beta-hydroxybutyrate is the predominant ketone body present in severe diabetic ketoacidosis. Different ketone tests measure one or more ketone bodies, and their results are not interchangeable. (See the "What is being tested?" section for more.)

Blood ketones are sometimes ordered, along with other tests such as blood gases, glucose, and electrolytes, to detect ketoacidosis in non-diabetics if they have signs and symptoms of DKA due to, for example, ingestion of excessive amounts of alcohol.

When is it ordered?

Blood ketone tests may be ordered when someone with diabetes has symptoms associated with diabetic ketoacidosis (DKA) and may also be performed whenever there is the potential for DKA to develop, such as when a diabetic is sick or pregnant. With the availability of home monitoring, blood ketones can be ordered as frequently as the person's healthcare provider recommends. Some signs and symptoms of ketoacidosis include:

  • Increased urination, excessive thirst
  • Dehydration, loss of electrolytes
  • Rapid breathing, shortness of breath
  • Fruity scent to the breath
  • Nausea, vomiting
  • Fatigue
  • Confusion
  • Coma (sometimes)

In non-diabetics, blood ketones are usually ordered when a person has symptoms associated with ketosis or ketoacidosis.

What does the test result mean?

If blood ketone levels are increased, then the person has some degree of ketosis or ketoacidosis.

If levels are low or normal, then the person either does not have excess ketone production or the ketone body that is elevated is not being detected by the test method used.

Is there anything else I should know?

Recent studies have shown that serum ketones and beta-hydroxybutyrate testing are both effective in diagnosing diabetic ketoacidosis (DKA). Some healthcare practitioners prefer beta-hydroxybutyrate. In acute DKA, the ketone body ratio (beta-hydroxybutyrate:acetoacetate) rises from normal (1:1) to as high as 10:1. In response to insulin therapy, beta-hydroxybutyrate levels commonly decrease long before acetoacetate levels. However, beta-hydroxybutyrate is not available in all laboratories.



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