A blood sugar test measures the amount of a sugar called glucose in a sample of your blood. Glucose is a major source of energy for most cells of the body, including brain cells. Glucose is a building block for carbohydrates. Carbohydrates are found in fruit, cereal, bread, pasta, and rice. Carbohydrates are quickly turned into glucose in your body. This can raise your blood glucose level.
Hormones made in the body help control blood glucose level.
Blood Sugar Random; Blood sugar level; Blood Sugar Fasting; Glucose test; Diabetic screening – blood sugar test; Diabetes – Sugar test
How the Test is Performed
Blood Sample Needed
How to Prepare for the Test
- After you have not eaten anything for at least 8 hours (fasting)
- At any time of the day (random)
- Two hours after you drink a certain amount of glucose.
Types Of Blood Sugar
Type 1 diabetes,
Type 2 diabetes,
And a condition known as prediabetes
Type 1 diabetes symptoms often start suddenly and are often the reason for checking blood sugar levels. Because symptoms of other types of diabetes and prediabetes come on more gradually or may not be easy to see, the American Diabetes Association (ADA) has developed screening guidelines. Anyone with a body mass index higher than 25 (23 for Asian Americans), regardless of age, who has additional risk factors. These factors include high blood pressure, non-typical cholesterol levels, an inactive lifestyle, a history of polycystic ovary syndrome or heart disease, and having a close relative with diabetes.
Anyone older than age 35 is advised to get an initial blood sugar screening. If the results are normal, they should be screened every three years after that.
Women who have had gestational diabetes are advised to be screened for diabetes every three years.
Anyone who has been diagnosed with prediabetes is advised to be tested every year.
Anyone who has HIV is advised to be tested.
Test for type 1 and type 2 diabetes and prediabetes
Glycated hemoglobin (A1C) test. This blood test, which doesn’t require not eating for a period of time (fasting), shows your average blood sugar level for the past 2 to 3 months. It measures the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells.
The higher your blood sugar levels, the more hemoglobin you’ll have with sugar attached. An A1C level of 6.5% or higher on two separate tests means that you have diabetes. An A1C between 5.7% and 6.4% means that you have prediabetes. Below 5.7% is considered normal.
Random blood sugar test. A blood sample will be taken at a random time. No matter when you last ate, a blood sugar level of 200 milligrams per deciliter (mg/dL) — 11.1 millimoles per liter (mmol/L) — or higher suggests diabetes.
Fasting blood sugar test. A blood sample will be taken after you haven’t eaten anything the night before (fast). A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is normal. A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes. If it’s 126 mg/dL (7 mmol/L) or higher on two separate tests, you have diabetes.
Oral glucose tolerance test. For this test, you fast overnight. Then, the fasting blood sugar level is measured. Then you drink a sugary liquid, and blood sugar levels are tested regularly for the next two hours.
A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal. A reading of more than 200 mg/dL (11.1 mmol/L) after two hours means you have diabetes. A reading between 140 and 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) means you have prediabetes.
Advised Test of Sugar
Fasting plasma glucose test. The doctor tests your blood sugar levels after fasting for 8 hours and it’s higher than 126 mg/dL.
Oral glucose tolerance test. After fasting for 8 hours, you get a special sugary drink. Two hours later your sugar level is higher than 200.
Random check. The doctor tests your blood sugar and it’s higher than 200, plus you’re peeing more, always thirsty, and you’ve gained or lost a significant amount of weight. They’ll then do a fasting sugar level test or an oral glucose tolerance test to confirm the diagnosis.
Any sugar levels high than normal are unhealthy. Levels that are higher than normal, but not reaching the point of full-blown diabetes, are called prediabetes.
Sugar and Your Body
Why are high blood sugar levels bad for you? Glucose is precious fuel for all the cells in your body when it’s present at normal levels. But it can behave like a slow-acting poison.
High sugar levels slowly erode the ability of cells in your pancreas to make insulin. The organ overcompensates and insulin levels stay too high. Over time, the pancreas is permanently damaged.
High levels of blood sugar can cause changes that lead to a hardening of the blood vessels, what doctors call atherosclerosis.
Almost any part of your body can be harmed by too much sugar. Damaged blood vessels cause problems such as:
1.Kidney disease or kidney failure, requiring dialysis
4.Vision loss or blindness
5.Weakened immune system, with a greater risk of infections
Nerve damage, also called neuropathy, that causes tingling, pain, or less sensation in your feet, legs, and hands
Poor circulation to the legs and feet
Slow wound-healing and the potential for amputation in rare cases.
Why the Test is Performed
Your doctor may order this test if you have signs of diabetes. More than likely, the doctor will order a fasting blood sugar test.
The blood glucose test is also used to monitor people who already have diabetes.
The test may also be done if you have:
An increase in how often you need to urinate
Recently gained a lot of weight
Confusion or a change in the way you normally talk or behave
Seizures (for the first time)
Unconsciousness or coma
Screening for Blood Sugar
This test may also be used to screen a person for diabetes.
High blood sugar and diabetes may not cause symptoms in the early stages. A fasting blood sugar test is almost always done to screen for diabetes.
If you are over age 45, you should be tested every 3 years.
If you’re overweight (body mass index, or BMI, of 25 or higher) and have any of the risk factors below, ask your health care provider about getting tested at an earlier age and more often:
High blood sugar level on a previous test
Blood pressure of 140/90 mm Hg or higher, or unhealthy cholesterol levels
History of heart disease
Member of a high-risk ethnic group (African American, Latino, Native American, Asian American, or Pacific Islander)
Woman who has been diagnosed with gestational diabetes
Polycystic ovary disease (condition in which a woman has an imbalance of female sex hormones causing cysts in the ovaries)
Close relative with diabetes (such as a parent, brother, or sister)
Not physically active
Children age 10 and older who are overweight and have at least two of the risk factors listed above should be tested for type 2 diabetes every 3 years, even if they have no symptoms.
If you had a fasting blood glucose test, a level between 70 and 100 mg/dL (3.9 and 5.6 mmol/L) is considered normal.
If you had a random blood glucose test, a normal result depends on when you last ate. Most of the time, the blood glucose level will be 125 mg/dL (6.9 mmol/L) or lower.
The examples above show the common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
If you had a fasting blood glucose test:
A level of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) means you have impaired fasting glucose, a type of prediabetes. This increases your risk of developing type 2 diabetes.
A level of 126 mg/dL (7 mmol/L) or higher usually means you have diabetes.
If you had a random blood glucose test:
A level of 200 mg/dL (11 mmol/L) or higher often means you have diabetes.
Your provider will order a fasting blood glucose, A1C test, or glucose tolerance test, depending on your random blood glucose test result.
In someone who has diabetes, an abnormal result on the random blood glucose test may mean that the diabetes is not well controlled.
Other medical problems can also cause a higher-than-normal blood glucose level, including:
Overactive thyroid gland
Swelling and inflammation of the pancreas (pancreatitis)
Stress due to trauma, stroke, heart attack, or surgery
Rare tumors, including pheochromocytoma, acromegaly, Cushing syndrome, or glucagonoma
A lower-than-normal blood glucose level (hypoglycemia) may be due to:
Hypopituitarism (a pituitary gland disorder)
Underactive thyroid gland or adrenal gland
Tumor in the pancreas (insulinoma – very rare)
Too little food
Too much insulin or other diabetes medicines
Liver or kidney disease
Weight loss after weight loss surgery