Random Blood Glucose Test

A random blood glucose test is used to diagnose diabetes. The test measures the level of glucose (a type of sugar) in your blood. If your blood glucose level is 200 mg/dL or higher and you have the classic symptoms of high blood sugar (excessive thirst, urination at night, blurred vision and, in some cases, weight loss) your doctor may diagnose you with diabetes. If you do not have any symptoms of high blood sugar, your doctor will probably have you take another test for further evidence of diabetes.1

Usually, having high blood glucose can be a sign that your body is not functioning normally and that you may have diabetes. If you have high blood glucose and it is not treated, it can lead to serious health complications. However, finding out that your blood glucose is elevated is powerful information that you can use to keep yourself healthy. If you know that your blood glucose is high, you can take steps to lower it, by losing weight (if you are overweight or obese), getting regular moderate physical activity, and taking a medication that lowers blood glucose.2

Why measuring blood glucose is important in diagnosing type 2 diabetes

Our bodies require energy to function properly and we get that energy from the foods we eat. Our diet (everything we eat and drink) includes three main sources of energy (also known as calories): protein, fat, and carbohydrates (sugars, starches, and fibers).When the body digests most sources of carbohydrates, they are transformed through digestion into a very important source of instant energy, a form of sugar called glucose. Our bodies depend on the action of a number of different natural body chemicals called hormones, including insulin, amylin, incretins, and glucagon, working together in conjunction, to control how we use glucose. In type 2 diabetes, these hormones no longer work in the way they should and this results in elevated blood glucose3-7

How is a random blood glucose test done?

A random blood glucose test requires taking a sample of blood. Unlike with a fast blood glucose test, there is no requirement for fasting before the blood sample is taken.8

Someone at your doctor’s office or the clinic where you are having the test done will take a sample of your blood by inserting a needle into your vein. The test is quick and there should be minimal discomfort

What do the results of a random blood glucose test mean?

Blood glucose levels will fluctuate widely during the day depending on when you take your meals and what you eat. So, results from a random blood glucose test will depend on when during the day you take the test. Normally, a person’s blood glucose level should be under 125 mg/dL. You may start your day at below 100 mg/dL in the morning before breakfast and your blood glucose may rise as high as 140 mg/dL about 2 hours after meals during the day. The table below shows a typical range of fluctuation for blood glucose levels for a person with diabetes and someone without diabetes.9

Random blood glucose test results

Time of test

Normal ranges for someone without diabetes

Goal ranges for someone with diabetes

Before breakfast (fasting) Less than 100 mg/dL 70–130 mg/dL
Before meals (lunch, supper, snack) LLess than 110 mg/dL 70–130 mg/dL
2 hours after meals Less than 140 mg/dL Less than 180 mg/dL
Bedtime Less than 120 mg/dL 90–150 mg/dL
Hemoglobin A1C results <6% <7%

Adapted from Goals for Blood Glucose Control. Joslin Diabetes Center. Available at: http://www.joslin.org/info/goals_for_blood_glucose_control.html. Accessed on 101614.

Can health conditions other than diabetes cause high blood glucose?

There are other health conditions that can cause high blood sugar. These include overactive thyroid gland, inflammation of the pancreas (pancreatitis), pancreatic cancer, and several rare tumors. Additionally, taking certain medications, such as steroids, can cause your blood sugar to become elevated.10

Written by: Jonathan Simmons | Last reviewed: May 2014.
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