A random glucose test is one way a doctor can measure how much glucose or sugar a person has circulating in their blood. Doctors use the result of random glucose testing to determine if a person may have diabetes.

This article will look at what a random glucose test is, why a doctor may recommend it, and what the results can mean.

What is random glucose testing?

glucose test
A random glucose test measures the amount of glucose or sugar in a person’s blood.

Glucose is a form of sugar and comes from the foods people eat. It is the body’s primary energy source and fuels every cell, including those in the brain, heart, and muscles.

The body is continually working to keep the amount of glucose in the blood at optimum levels. It does this by producing a hormone called insulin, which helps glucose get into the cells that need it for energy.

People with type 1 diabetes do not produce insulin because their immune systems attack and destroy the cells in the pancreas that make the insulin.

People with type 2 diabetes either do not produce enough insulin or their body does not respond to it appropriately.

When a person does not make insulin correctly, glucose stays in their blood. Medical professionals call too much sugar in the blood hyperglycemia, while they refer to too little sugar in the blood as hypoglycemia.

Random glucose testing is one way of checking the levels of glucose in the blood. Doctors may carry out a random glucose test at any time of the day.

If the result indicates that a person has higher than expected glucose levels, the doctor will usually order a follow-up test to confirm the diagnosis. This may be another random glucose test, or it may be a:

  • Fasting glucose test. This checks the levels of glucose in the blood after the person has had nothing to eat or drink for 8 hours. Doctors usually perform this test in the morning, before breakfast.
  • Oral glucose tolerance test (OGTT). People with diabetes can sometimes have a typically normal fasting or random glucose test. If a doctor still suspects diabetes, they may recommend an OGTT. This test also requires a person not to eat or drink for 8 hours. After giving the first blood sample, the individual drinks a liquid containing glucose, and then more blood samples are taken hourly over the course of the next 2 hours.

How and when is the test done?

A doctor may recommend a random blood glucose test if a person has symptoms of diabetes, such as:

  • urinating more often
  • feeling extremely thirsty
  • feeling very hungry despite eating enough
  • unexplained weight loss
  • extreme fatigue or tiredness
  • blurred vision
  • slow healing of cuts and bruises

Type 2 diabetes can often develop slowly, which can make symptoms difficult to detect at first.

People with diabetes may also experience a sensation of tingling or numbness in the hands or feet, which is known as diabetic neuropathy. This is more likely to occur if a person’s blood glucose remains uncontrolled for extended periods.

A random glucose test is a quick test that a doctor or nurse can carry out at short notice in their office or clinic. The person does not need to fast beforehand.

The test requires a small sample of blood that the doctor or nurse will take using a needle.

What do the results mean?

salad weights and tape measure
Making dietary changes and losing weight can help people with prediabetes reduce their risk of developing diabetes.

Doctors measure the amount of glucose in a person’s blood in milligrams per deciliter or mg/dL.

For a random glucose test, a result of 200 mg/dL or above indicates that a person may have diabetes. However, for a more reliable diagnosis, the doctor will usually repeat the test on another day.

To help confirm the diagnosis, the doctor may also order a different type of test, such as a fasting glucose test or an OGTT.

For a fasting glucose test:

  • less than 100 mg/dL is normal
  • 100 to 125 mg/dL indicates prediabetes
  • 126 mg/dL or above indicates diabetes

For an OGTT:

  • less than 140 mg/dL is normal
  • 140 to 199 mg/dL indicates prediabetes
  • 200 mg/dL or above indicates diabetes

Prediabetes means that a person’s blood glucose levels are higher than usual, but doctors do not yet consider that they have diabetes. Doctors sometimes call this impaired glucose tolerance (IGT) or impaired fasting glucose (IFG).

People with prediabetes are at increased risk of developing diabetes. Lifestyle modifications, such as weight loss and exercise, and certain medications can help reduce this risk.

What can affect the result?

Blood glucose levels change throughout the day, depending on factors such as what a person has eaten and how much exercise they have done that day. However, the blood glucose levels of people without diabetes tends to stay within the normal range.

The following factors may increase a person’s blood glucose levels:

  • eating too much food
  • low physical activity
  • medication side effects
  • illness
  • stress
  • pain
  • menstruation
  • dehydration

The following factors may decrease a person’s blood glucose levels:

  • eating little or no food
  • drinking alcohol
  • medication side effects
  • intense physical activity or exercise


woman having dental treatment
Untreated diabetes can lead to dental disease.

Diabetes is a chronic condition that, if left untreated, can lead to serious health problems and complications, including:

However, with effective treatment and management, people with diabetes can enjoy a healthy life.

Doctors usually diagnose type 1 diabetes in children and young adults. People with type 1 diabetes need to take insulin daily and regularly monitor their blood sugar levels for the rest of their lives.

Type 2 diabetes often develops later in life. A person can sometimes manage type 2 diabetes with just diet and exercise. Other people may need medication or even insulin so that they can keep their blood sugar levels within healthy levels.

Anyone with symptoms of diabetes should see their doctor for an evaluation.