If a person is surprised about their blood sugar results, it may be that some factor — such as a damaged test strip — has produced a falsely high reading. It may also be a sign of an underlying health condition.

Blood glucose tests can help track the amount of sugar present in the bloodstream. Certain factors may cause these tests to yield false high blood sugar readings. Dirty glucose meters, unwashed hands, or damaged test strips can all lead to false test results.

During digestion, the body sends sugar taken from food into the blood. Cells throughout the body use this sugar for fuel or store it for future use. Individuals with conditions like diabetes may have too much or too little sugar circulating through their blood.

Blood glucose meters and continuous glucose monitors provide real-time blood sugar readings. While these readings are generally accurate, they may occasionally provide false results.

This article explores what factors can cause false high blood sugar results. Keep reading to learn more about what influences blood sugar and how to prevent inaccurate testing results.

What is diabetes?

Learn more about diabetes through our dedicated diabetes hub.

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When used properly, modern blood sugar testing equipment generally yields accurate readings. But damaged meters or contaminated tests may produce false high blood sugar readings.

Faulty equipment

Faulty blood glucose meters or user error can both produce false high readings. These meters may yield false high blood sugar readings if:

  • not properly calibrated
  • used incorrectly
  • dirty or damaged
  • batteries are not functioning correctly

Using the wrong test strips for a given meter can also lead to false results. And pre-owned test strips can influence blood sugar readings. These strips may have expired or experienced contamination from a previous owner.

Unwashed hands

Unwashed hands can cause false high blood sugar readings. In one study, researchers examined blood sugar readings among individuals who had just handled fruit. If they did not wash their hands, these individuals had false high blood sugar readings.

Even cleaning their fingertips with an alcohol swab did not prevent false readings. Washing the hands with soap and water is crucial for receiving accurate results from a finger-prick test.

Other causes

Other factors may also influence the results of a blood sugar test.

They may include:

  • temperature
  • high altitudes
  • high levels of acetaminophen in the blood
  • improper storage of testing equipment

In addition to acetaminophen, medications that contain ascorbic acid, dopamine, mannitol, and icodextrin can also influence results. Anyone performing regular blood sugar testing should speak with a doctor to learn more.

What are some reasons for blood sugar spikes?

Many different factors can elevate blood sugar. These may include:

Many people also experience a hormone surge in the early morning. This “dawn phenomenon” can lead to elevated blood sugar in people with diabetes. Certain illnesses like gum disease can also increase blood sugar levels.

Some medications can influence blood sugar. For example, according to Alberta Health Services, taking steroids typically elevates blood sugar within 4 to 8 hours.

Researchers have also found that menstruation can affect blood sugar levels. People with type 1 diabetes may experience elevated blood sugar levels between 3 and 5 days before their period, according to Diabetes UK. Sugar levels may also fall during this time and then return to normal levels after a period begins.

Active individuals can experience lower blood sugar levels after exercise. Exercising can reduce blood sugar for a day or longer depending on the person.

Each individual living with diabetes may have a unique reaction to factors that affect blood sugar levels. It is important to regularly check blood sugar levels. This can help determine how the body reacts to different factors and make it easier to stabilize blood sugar over time.

What are healthy blood sugar levels?

People who need to measure blood sugar regularly typically use either a blood glucose meter or a continuous glucose monitoring device (GCM). Let’s review how each of these devices works.

Blood glucose meter

Before using a blood glucose meter, make sure that the meter is clean and functioning properly. Wash hands thoroughly with soap and water.

Using a lancet, prick the finger. Begin squeezing the finger from the base until a drop of blood forms on the fingertip surface. Transfer a small amount of this blood onto a test strip and insert the test strip into the meter.

Once the meter analyzes the blood sample, it will display a blood sugar reading. After viewing and recording this reading, dispose of the test strip and lancet.

What can we learn from a blood glucose chart?

Continuous glucose monitoring device

A continuous glucose monitor (CGM) uses a sensor beneath the skin to monitor blood sugar continuously. Before using a GCM, speak with a doctor to learn more about how and where to insert this sensor.

When using a GCM, be sure to replace the sensor regularly. Each sensor typically lasts 3–7 days, depending on the individual and the GCM model.

A GCM device measures blood sugar levels every few minutes. Each device includes a wireless transmitter that delivers blood sugar readings to a monitor. Some GCM models can send readings to a tablet or smartphone, making these devices an excellent choice for active individuals.

How do you test for diabetes at home?

Factors that influence blood sugar levels vary widely between individuals. Keeping track of blood sugar can help determine what factors raise or lower levels. This can make it easier to manage blood sugar over time.

Other methods for managing blood sugar may include:

Following a health-promoting lifestyle can help stabilize blood sugar levels over time. Anyone looking for additional information about managing blood sugar can speak with a doctor to learn more.

Get some more tips on lowering blood sugar levels here.

Certain factors may cause false high blood sugar readings. Unwashed hands, faulty equipment, or environmental conditions can all play a role. Some health factors and dietary factors can also contribute.

To help avoid a false high blood sugar reading, ensure that testing equipment is in good working order. If a test continues to yield false readings, speak with a doctor to learn more about what may be causing these errors.

Testing blood sugar regularly is an important part of managing blood sugar. Eating a varied and nutritious diet and exercising consistently can also help promote stable blood sugar levels.