What is Random Glucose Testing?


A random glucose test is one method for measuring the amount of glucose or sugar circulating in a person’s blood. Doctors perform this test and use the result to find out whether a person is likely to have diabetes. While other tests may be necessary to confirm a full diagnosis, a random glucose test may help a doctor determine if additional testing is needed.


What is random glucose Testing?

Random glucose testing measures a person’s blood glucose levels at any given point in the day, randomly. Blood glucose is also known as blood sugar. Many blood tests for diabetes involve either fasting or continuous monitoring, but this test does not. It is useful for people who need a speedy diagnosis, such as those with type 1 diabetes who require urgent supplementary insulin.


How does the test work?

Glucose is a form of sugar. It is the body’s primary energy source and fuel for every cell which includes brain, heart, and muscles. It generally comes from food and drink people consume. In fasting, body also breaks down stored forms of carbohydrate (glycogen) into glucose. The body works uninterrupted to keep the optimum level of blood glucose for functioning. It produces a hormone called insulin to achieve this, which regulate glucose get into the cells which is need for energy.

A person with type 1 diabetes does not produce insulin as their body no longer makes insulin.

Someone with type 2 diabetes either does not produce enough insulin, or their body does not respond to it appropriately i.e. they develop resistance.

When a person does not make insulin correctly, glucose remains in the blood. Hyperglycaemia occurs when levels remain consistently high, and hypoglycaemia occurs when they are too low. Random glucose testing is one way of checking those glucose levels in the blood. Doctors / patients (diabetics) can perform this test at any time of day.

If the result indicates that a person has higher than expected glucose levels, the doctor will typically order a follow-up test to confirm the diagnosis. This can include:

  • Fasting glucose test: This measures blood glucose levels 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 demonstrate normal results in the fasting or random glucose tests yet still have diabetes. If a doctor still suspects that a person has diabetes, they may recommend an OGTT. This test also requires that a person not eat or drink for 8 hours. After an initial blood sample, the individual drinks a liquid containing 75gm of glucose. The doctor then takes more blood samples hourly over the next 2 hours.

Reasons for Testing

A doctor may recommend a random blood glucose test if a person shows symptoms of diabetes.

These symptoms may include:

  • 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 might make initial symptoms difficult to detect.

People with diabetes may also experience a sensation of tingling or numbness in the hands or feet, called diabetic neuropathy. This is more likely to occur if a person does not control blood glucose for extended periods.



A random glucose test is a quick test that a doctor/nurse or patient can perform at short notice in their clinic or office/home. The person does not need to fast beforehand. The test requires a small blood sample using a needle, often from the finger.


What does the test mean?

Doctors measure the amount of glucose in a person’s blood in milligrams per deciliter (mg/dl).

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

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

  • Normal: less than 100 mg/dl
  • Pre-diabetes: 100–125 mg/dl
  • Diabetes: 126 mg/dl or above

Results of an OGTT indicate the following:

  • Normal: less than 140 mg/dl
  • Pre-diabetes: 140–199 mg/dl
  • Diabetes: 200 mg/dl or above

One 2015 study suggests that one random glucose test with a reading of over 100 mg/dl is a greater risk factor for diabetes than traditional factors, such as obesity.

Pre-diabetes 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 pre-diabetes 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 results?

Blood glucose levels change throughout the day, depending on various factors. These might include a person’s food intake, as well as the duration and intensity of any exercise or physical activity that day.

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

  • eating too much food
  • low levels of 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



Diagnosis with any chronic condition can be distressing, and, without treatment, diabetes can lead to serious health problems and complications. These can include:

  • heart disease
  • stroke
  • chronic kidney disease
  • vision problems
  • oral health issues
  • nerve damage

However, with effective treatment and management, people with diabetes can enjoy a long and active 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 glucose levels for life.

Type 2 diabetes often develops later in life. A person can sometimes manage type 2 diabetes using only diet and exercise. Other people may need medication or insulin to keep their blood glucose levels within the healthy range.


A random glucose test measures the amount of glucose or sugar circulating in a person’s blood. They will not need to fast before the test takes place.

Doctors perform this test to determine whether a person may have diabetes. A random glucose test may help a doctor establish if additional testing is needed to make a full diagnosis.

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