Diabetes is a chronic disease characterized by high levels of blood glucose (or blood sugar), which leads over time to serious damage to the heart, blood vessels, eyes, kidneys and nerves. There are two types of diabetes, type1 and type 2. The most common is type 2 diabetes, usually in adults, which occurs when the body becomes resistant to the glucose regulatory hormone, insulin or does not make enough of the insulin. According to the WHO, in the past three decades the cases of diabetes has risen dramatically in countries of all income levels. They estimate that about 422 million people worldwide have diabetes, the majority living in low-and middle-income countries, and 1.5 million deaths are directly attributed to diabetes each year. This means that almost everyone knows someone with diabetes!
What are the symptoms of diabetes?
The symptoms of diabetes and its complications span across different organ systems, literally from the head to the toe! However, the common symptoms generally are: Increased thirst, frequent urination, extreme hunger, unexplained weight loss, fatigue, irritability, blurred vision, slow-healing sores, and frequent infections, such as gums or skin infections and vaginal infections. It can cause coma and death in extreme situations.
How to test for diabetes
There are several tests to carry out if one is suspected to have diabetes. All these tests are done with a blood sample. They are:
- The Fasting blood sugar
- The Random blood sugar
- The oral glucose tolerance test and
- The HBA1c test
What is a fasting blood sugar test?
A fasting blood sugar test measures the amount of sugar (glucose) in the blood. It is a common, simple, very safe method of estimating blood sugar usually done after an overnight fast.
It can be done at home, in the lab, or health care providers office. In the lab, it is done with a blood draw. A healthcare provider will draw blood from a vein into a clean vial and sent to the lab for analysis.
In other cases, it can be done with a prick on the finger instead of a needle in the vein. The drop of blood is placed in a glucometer test strip to estimate the blood glucose level. This can be done at home or in the doctor’s office.
Preparation for Fasting Blood Sugar test.
No special preparation is required for this test, however, the person is not to take food, fruits, juices or anything by mouth, including medications for at least 8 hours (usually 8 to 12 hours) before the test. In normal situations, this usually corresponds to the period just before breakfast.
Can water be taken before a Fasting Blood Sugar test?
Water contains no carbohydrate or calories and so can safely be taken during the 8 hour fast before doing a fasting blood sugar test. Basically it has no effect on the result. However, studies have shown that the blood sugar is usually higher if a person is dehydrated and drinking enough water has been associated with lower blood glucose levels and delay of onset of high blood glucose. Based on this therefore, drinking a significant amount of water just before a fasting blood sugar can potentially give a lower value. This may not be significant as there is no guideline prohibiting people from drinking water just before a test. In summary, if one is thirsty and cannot wait after the test to drink water, there is no harm in drinking water to quench the thirst.
What of other fasting blood tests?
The same rule applies for other fasting blood tests like the fasting lipid tests for checking the level and types of lipids or cholesterol in the blood. However, unlike sugar test, there seems to be no effect with drinking water just before the test.
What is the science behind Fasting Blood Sugar?
During fasting, when a person has not eaten for about eight hours and there is no food coming in to be broken down to glucose, the body is perceived to be in the fasting phase. During this phase, an important hormone called glucagon is released and insulin is reduced. The insulin: glucagon ratio will tilt towards glucagon. This hormone helps to increase blood sugar levels for the body to continue its metabolic activities. However, in a normal person, enough insulin is released to check the effects of glucagon and keep the blood sugar at a normal level. If there is insulin resistance or reduction, the blood sugar will be high despite the fact that the person has not yet eaten.
How to interpret FBG tests
According to the American Diabetic Society, a Fasting Blood Sugar interpreted as follows:
Fasting Blood Glucose value of between 70mg/dl to 100mg/dl or 3.9 to 5.6 mmol/l is considered normal
A value of between 100mg/dl to 125mg/dl (5.6momol/l to 6.9mmol/l) is interpreted as prediabetes.
A value greater than 126mmol/l or 7mmol/l is considered to be diabetes.
This test has to be done at least twice in the presence of other symptoms or clinical suspicion of diabetes before a diagnosis of diabetes is confirmed.
Other tests for blood sugar.
The other tests for blood sugar listed above are also important to diagnose diabetes. The HbA1c has been advocated as the standard for diagnosing Diabetes as well as monitoring long term sugar control. This is combined with the fasting blood sugar for day to day control of blood sugar. Other tests like the two-hour post prandial and random blood sugar tests can be used in different situations, and fasting for 8 hours is not necessary for then, although like the name suggests, the two-hours post prandial will require a 2-hour period of fasting before it is done. The cut off values for these tests also differ in normal individuals, people with pre-diabetes, and people with diabetes.
If you have diabetes, notice the symptoms of diabetes or are in doubt if you should do a fasting blood sugar test, please contact your healthcare provider for guidance.