Many types of glucose tests exist and they can be used to estimate

blood sugar levels The blood sugar level, blood sugar concentration, blood glucose level, or glycemia is the measure of glucose concentrated in the blood. The body tightly regulates blood glucose levels as a part of metabolic homeostasis. For a 70 kg (15 ...

at a given time or, over a longer period of time, to obtain average levels or to see how fast the body is able to normalize changed

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

levels. Eating food for example leads to elevated blood sugar levels. In healthy people, these levels quickly return to normal via increased cellular glucose uptake which is primarily mediated by increase in blood

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...

levels. Glucose tests can reveal temporary/long-term

hyperglycemia Hyperglycemia is a condition where unusually high amount of glucose is present in blood. It is defined as blood glucose level exceeding 6.9 mmol/L (125 mg/dL) after fasting for 8 hours or 10 mmol/L (180 mg/dL) 2 hours after eating. Blood gluc ...

hypoglycemia Hypoglycemia (American English), also spelled hypoglycaemia or hypoglycæmia (British English), sometimes called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's tria ...

. These conditions may not have obvious symptoms and can damage organs in the long-term. Abnormally high/low levels, slow return to normal levels from either of these conditions and/or inability to normalize blood sugar levels means that the person being tested probably has some kind of medical condition like

type 2 diabetes Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent ...

which is caused by cellular insensitivity to insulin. Glucose tests are thus often used to diagnose such conditions.

Testing methods

Tests that can be performed at home are used in

blood glucose monitoring Blood glucose monitoring is the use of a glucose meter for testing the concentration of glucose in the blood (Blood sugar level, glycemia). Particularly important in diabetes management, a blood glucose test is typically performed by piercing ...

for illnesses that have already been diagnosed medically so that these illnesses can be maintained via medication and meal timing. Some of the home testing methods include *

fingerprick In medicine, some blood tests are conducted on capillary blood obtained by fingerstick (or fingerprick) (or, for neonates, by an analogous heelprick). The site, free of surface arterial flow, where the blood is to be collected is sterilized with a ...

type of

glucose meter A glucose meter, also referred to as a "glucometer", is a medical device for determining the approximate concentration of glucose in the blood. It can also be a strip of glucose paper dipped into a substance and measured to the glucose chart. ...

- need to prick self finger 8-12 times a day. *

continuous glucose monitor A continuous glucose monitor (CGM) is a device for monitoring blood glucose continuously instead of monitoring periodically by drawing a drop of blood from a finger. This is known as continuous glucose monitoring. CGMs are used by people who trea ...

- the CGM monitors the glucose levels every 5 minutes approximately. Laboratory tests are often used to diagnose illnesses and such methods include * fasting blood sugar (FBS), fasting plasma glucose (FPG): 10–16 hours after eating *

glucose tolerance test The glucose tolerance test (GTT, not to be confused with GGT test) is a medical test in which glucose is given and blood samples taken afterward to determine how quickly it is cleared from the blood. The test is usually used to test for diabetes, ...

: continuous testing *

postprandial glucose test A postprandial glucose (PPG) test is a blood glucose test that determines the amount of glucose in the plasma after a meal. The diagnosis is typically restricted to ''postprandial hyperglycemia'' due to lack of strong evidence of co-relation wit ...

(PC): 2 hours after eating *

random glucose test A random glucose test, also known as a random blood glucose test (RBG test) or a casual blood glucose test (CBG test) is a glucose test (test of blood sugar level) on the blood of a non-fasting person. This test assumes a recent meal and therefor ...

Some laboratory tests don't measure glucose levels directly from body fluids or tissues but still indicate elevated blood sugar levels. Such tests measure the levels of

glycated hemoglobin Glycated hemoglobin, also called glycohemoglobin, is a form of hemoglobin (Hb) that is chemically linked to a sugar. Most monosaccharides, including glucose, galactose, and fructose, spontaneously (that is, non-enzymatically) bond with hemoglob ...

, other glycated proteins, 1,5-anhydroglucitol etc. from blood.

Use in medical diagnosis

Glucose testing can be used to diagnose or indicate certain medical conditions.

High blood sugar Hyperglycemia is a condition where unusually high amount of glucose is present in blood. It is defined as blood glucose level exceeding 6.9 mmol/L (125 mg/dL) after fasting for 8 hours or 10 mmol/L (180 mg/dL) 2 hours after eating. Blood gluco ...

may indicate *

gestational diabetes Gestational diabetes is a condition in which a woman without diabetes develops hyperglycemia, high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms. Obesity increases the rate of pre-eclampsia, cesarea ...

. This temporary form of diabetes appears during pregnancy, and with glucose-controlling medication or

symptoms can be improved. * type 1 and

prediabetes Prediabetes is a component of metabolic syndrome and is characterized by elevated blood sugar levels that fall below the threshold to diagnose diabetes mellitus. It usually does not cause symptoms, but people with prediabetes often have obesity ( ...

. If diagnosed with diabetes, regular glucose tests can help manage or maintain conditions. Type 1, is commonly seen in children or teenagers whose bodies are not producing enough insulin. Type 2 diabetes, is typically seen in adults who are overweight. The insulin in their bodies are either not working normally, or there is not being enough produced.

Low blood sugar Hypoglycemia (American English), also spelled hypoglycaemia or hypoglycæmia (British English), sometimes called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's tria ...

may indicate * insulin overuse *

starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, de ...

* underactive thyroid *

Addison's disease Addison's disease, also known as primary adrenal insufficiency, is a rare long-term endocrine disorder characterized by inadequate production of the steroid hormones cortisol and aldosterone by the two outer layers of the cells of the adr ...

insulinoma An insulinoma is a tumour of the pancreas that is derived from beta cells and secretes insulin. It is a rare form of a neuroendocrine tumour. Most insulinomas are benign in that they grow exclusively at their origin within the pancreas, but a m ...

kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an Inflammation, inflammatory kidney disease and has several types according to the location of the inflammation. Infla ...

Preparing for testing

Fasting Fasting is the act of refraining from eating, and sometimes drinking. However, from a purely physiological context, "fasting" may refer to the metabolic status of a person who has not eaten overnight (before "breakfast"), or to the metabolic sta ...

prior to glucose testing may be required with some test types. Fasting blood sugar test, for example, requires 10–16 hour-long period of not eating before the test. Blood sugar levels can be affected by some drugs and prior to some glucose tests these medications should be temporarily given up or their dosages should be decreased. Such drugs may include

salicylates Salicylic acid is an organic compound with the formula HOC6H4COOH. A colorless (or white), bitter-tasting solid, it is a precursor to and a metabolite of acetylsalicylic acid (aspirin). It is a plant hormone, and has been listed by the EPA Tox ...

(Aspirin),

birth control pills Oral contraceptives, abbreviated OCPs, also known as birth control pills, are medications taken by mouth for the purpose of birth control. The introduction of the birth control pill ("the Pill") in 1960 revolutionized the options for contraception, ...

corticosteroids Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invol ...

tricyclic antidepressants Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains ...

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

diuretics A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics in ...

and

phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anticonvulsant, anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence se ...

. Some foods contain

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...

(

coffee Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially a ...

tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of '' Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of south-western China and nor ...

cola Cola is a Carbonation, carbonated soft drink flavored with vanilla, cinnamon, citrus essential oil, oils, and other flavorings. Cola became popular worldwide after the American pharmacist John Stith Pemberton invented Coca-Cola, a trademarked br ...

energy drink An energy drink is a type of non-alcoholic psychoactive functional beverage containing stimulant compounds, usually caffeine (at a higher concentration than ordinary soda pop) and taurine, which is marketed as reducing tiredness and improving pe ...

s etc.). Blood sugar levels of healthy people are generally not significantly changed by caffeine, but in diabetics caffeine intake may elevate these levels via its ability to stimulate the

adrenergic nervous system Adrenergic means "working on adrenaline (epinephrine) or noradrenaline (norepinephrine)" (or on their receptors). When not further qualified, it is usually used in the sense of enhancing or mimicking the effects of epinephrine and norepinephrine i ...

Reference ranges

Fasting blood sugar

A level below 5.6 mmol/L (100 mg/dL) 10–16 hours without eating is normal. 5.6–6 mmol/L (100–109 mg/dL) may indicate

and

oral glucose tolerance test The glucose tolerance test (GTT, not to be confused with GGT test) is a medical test in which glucose is given and blood samples taken afterward to determine how quickly it is cleared from the blood. The test is usually used to test for diabetes, ...

(OGTT) should be offered to high-risk individuals (old people, those with

high blood pressure Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major ri ...

etc.). 6.1–6.9 mmol/L (110–125 mg/dL) means OGTT should be offered even if other indicators of diabetes are not present. 7 mmol/L (126 mg/dL) and above indicates diabetes and the fasting test should be repeated.

Testing methods

Use in medical diagnosis

Preparing for testing

Reference ranges

Fasting blood sugar

Glucose tolerance test

Postprandial glucose test

Random glucose test

See also

References