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Random Glucose Tests: Testing Stability

What Is Glucose Testing?

Glucose testing is a random blood test to check glucose levels. It is usually done by pricking the finger to draw a small drop of blood. This blood is then wiped onto a test strip that will give a glucose reading. This is a powerful tool for people with diabetes. It can help assess how well the disease is being managed.


Diabetes is a disease that affects your body’s ability to release insulin from your pancreas once sugars are turned into glucose. The insulin allows the glucose to enter the bloodstream and release energy. In diabetes, this function does not work properly.

Some early symptoms of diabetes are excessive urination and thirst. This is caused by the sugar buildup in the blood that is not absorbed. It is filtered out through the kidneys in large amounts, which can then lead to dehydration. Other symptoms may include weight loss, blurred vision, being tired constantly, tingling in arms and legs, sore gums, and slow healing.

Understanding Glucose Testing

Glucose testing helps keep track of symptoms and manage diabetes. Random blood glucose values vary depending on the last time you ate. If you are testing within one to two hours after the start of a meal, the American Diabetes Association (ADA) recommends glucose levels be under 180 mg/dL. Before a meal the levels can be between 80 and 130 mg/dL.

Normal glucose reading< 140 mg/dL
Chance of impaired glucose tolerance (prediabetes)140 mg/dL to 199 mg/dL
Chance of diabetes> 200 mg/dL

A normal glucose reading for someone without diabetes is lower than 140 mg/dL. If the reading is anywhere from 140 mg/dL to 199 mg/dL, there is a chance you suffer from impaired glucose tolerance. This is otherwise known as prediabetes, and there is a chance it can develop into type 2. If the reading is higher than 200 mg/dL, there is a high chance you have diabetes.

A doctor may schedule another glucose test for you if it is positive for diabetes. There are a number of factors that can contribute to an inaccurate reading, including certain medications or illnesses.

If you have diabetes, blood glucose levels are based on age, how long you’ve had it for, and the initial blood tests.

The ADA suggests keeping track of all the results to keep a daily record of blood level history. Stress, activity, and food can make the results vary, so keeping note of what you are doing or feeling with the levels is also crucial.

If the readings are too high or too low for a number of days in a row, it may be time to consult a doctor. Going over a target level with a doctor and changing the plan can give better results.

Random Glucose Testing and Disease Management

In adults without diabetes, glucose levels are managed through the actions of insulin and the body’s use of sugar for energy. If they received random glucose tests throughout the day, their glucose levels would remain relatively stable. This would be true even if they:

  • varied their diet
  • experienced stress
  • ate at different times of the day

In people with diabetes and prediabetes, glucose levels can vary widely over the course of the day. This is particularly true if the disease is not well-managed. In these people, random test results will vary widely. Tests may also be consistently high.

A random test is one performed outside your normal testing schedule. Random testing is an important part of diabetes management. If random glucose levels are acceptable, your strategy is probably working. Wide swings in your levels suggest you need to change your management plan.

Remember, high sugar levels are what cause the complications seen with diabetes over time. Symptoms of acute high blood sugar levels include:

  • increased thirst
  • increased nighttime urination
  • slow healing
  • blurry vision

When to Test

If you have diabetes, paying close attention to your symptoms is very important. Be sure to test immediately if you feel you are experiencing symptoms of low blood sugar. Random blood glucose readings can help you identify hyperglycemia and avoid any chronic complications. 

Testing your blood glucose levels at various times throughout the day can help you manage your diabetes and reduce your risk of complications. The only way you can know what your blood sugar level is to test it on a regular basis.

Other Types of Glucose Testing

Random glucose testing isn’t a substitute for your normal glucose testing schedule. You should also perform fasting tests and post-meal tests, as suggested by your doctor.

A fasting blood glucose test is usually performed upon waking, before you eat. Post-meal blood glucose tests measure glucose levels around two hours after the start of a meal. Different testing times will yield different results. These are affected by:

  • the food you’ve eaten
  • stress
  • medicines you’re taking
  • any exercise you have done

It’s important to test every day. This helps you get a sense of your overall blood sugar control and can help you make treatment decisions. Testing is the best way to learn how your blood sugar is affected by your lifestyle, medications, or both.

Random Glucose Testing and Exercise

Exercise can play a role in your random glucose test results. Generally, exercise will lower glucose levels. It may even require you to adjust your insulin regimen, if you’re on intensive insulin therapy. This should not discourage you from exercising. Exercise is one of the best ways you can help control diabetes. Most people with diabetes gain benefits from even moderate exercise.

Exercise increases your body’s ability to use insulin. It also burns extra glucose in your bloodstream. In the long term, exercise will lead to more stable random glucose test results.


Diabetes is a serious condition. There is no cure for it, but it can be managed with proper care. The key is healthy behavior changes combined with good glucose monitoring. If you find that your glucose levels just aren’t getting under control, it’s time to speak with your doctor. You may need to make changes in your management program before further complications arise. 

Content licensed from:

Written by: Brett Huffman and Justin Sarachik
Medically reviewed on: Mar 02, 2016: Mark R Laflamme, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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