Glucose Tests: A laboratory perspective

A glucose test is done to determine the levels of free glucose molecules in circulation.

Glucose is a simple sugar obtained when complex carbohydrates are broken down during digestion or artificially outside the body. It makes up the primary energy source for most cells in the body including the brain cells.

The concentration of this glucose in the body is regulated by hormones that facilitate its conversion to glycogen when in excess in the bloodstream and vice-versa. A problem with the effectiveness of these hormones could result in diabetes Mellitus. The hormones include insulin and glucagon with the former facilitating the conversion of glucose molecules to glycogen molecules and glucagon facilitating the breakdown of the glycogen molecules to glucose.

You must have heard of a diabetic patient talking about their insulin shot; well, insulin is a hormone that enables cells to take in glucose besides facilitating its storage through conversion to glycogen. It is produced by the pancreas and works on the liver cells.

Usually, after one has had a carbohydrate meal, the levels of blood glucose rise which triggers the release of this hormone into the bloodstream. on the other hand, during fasting, the release of glucagon is triggered to avail more glucose for utilization by the active cells.


Glucose tests are done before someone eats anything, randomly during the day perhaps after a meal, or as a controlled test that investigates the body’s tolerance to glucose as in the ability to regulate glucose levels in the blood known as the Oral Glucose Tolerance Test (OGTT).

The amount of glucose in urine should be undetectable in a healthy individual. If there is a high concentration of glucose in the urine, there might result in the rapid growth of microorganisms such as bacteria and fungi which can cause a lot of complications in the urinary system such as urinary tract infections and bladder infections.

Such complications can be avoided through living a healthy lifestyle which includes proper dieting and routine glucose tests to ensure that the body is effectively handling your sugars.

The glucose test curried out before one eats anything, fasting blood sugar can is used to determine the effectivity of Glucagon in facilitating the release of glucose into blood; this majorly depends on the length of time one has taken after taking their last meal. the random blood sugar, however, can be measured after one has taken a meal perhaps tea.

To measure tolerance, a patient is given controlled amounts of glucose dissolved in water about 75 milligrams after the initial blood glucose concentration is taken, (considered the baseline measurement), then the blood concentration measured after two hours at an interval of 30 minutes, together with the amount or volume of urine produced. The measuring is done by a glucometer which measures concentration gauging the amount of oxygen consumed by the glucose oxidase to convert glucose in the blood to gluconolactone.

The samples that can be used to test for glucose levels include urine, blood, and cerebrospinal fluid. The normal ranges in urine should be 0-0.8 millimoles per liter; in the blood, it should be between 5.6 to 6.9 millimoles per liter with a value below 5.6 for fasting blood glucose is considered normal, and in the cerebrospinal fluid it is supposed to be between 2.5 to 4.4 millimoles per liter.

Now that you have come this far, try questions 1, 3, and 5 in section A and question 3 in section B in this clinical chemistry test.