Synonym

• Blood sugar
• Blood glucose
• Fasting blood sugar
• FBS

Tubes

• Red, green, or gray top tube
• 1-5 mL of venous blood

Additional information

• 8-12 hrs fasting required for Fasting Blood Sugar (FBS)
• Sample to be drawn 2hrs after intake of food for Postprandial Blood Sugar (PPBS)
• Random Blood Sugar (RBS) can be done at any time of the day
• Mention the following on the lab request form:
• Time when the patient last consumed food
• Time of sample collection
• Time when last pretest dose of insulin or antidiabetic drug, if any, was taken
• Send the sample to laboratory immediately
• If delay is anticipated:
• Use plasma
• Gray top tube with oxalate and fluoride

Info

• Measures the concentration of glucose (sugar) in the blood
• Glucose is a simple six-carbon sugar (monosaccharide), which is the main source of energy to most cells of the body
• Blood glucose metabolism:
• Absorbed from the small intestine after breakdown of dietary carbohydrates
• Circulated throughout the body
• Excess glucose is stored as glycogen in the liver or muscle tissue
• Glycogen converted to glucose between meals and released into the blood
• Blood levels are regulated mainly by the following two hormones:
• Insulin
• Lowers the blood glucose levels
• Stimulates cellular membrane to transport glucose from the extracellular to the intracellular space
• Stimulates formation of glycogen and triglycerides
• Glucagon
• Elevates blood glucose levels
• Accelerates breakdown of glycogen to glucose
• Other hormones playing key roles in glucose metabolism:
• Adrenocorticotropic hormone (ACTH)
• Adrenocorticosteroids
• Epinephrine
• Thyroxine (T₄)
• Some cells such as red blood cells and brain cells are totally dependent on glucose as their energy source. These cells can only function when there is an adequate glucose level

Clinical

• The clinical utilities of blood glucose levels are:
• As a screening test for people who are at a high risk of developing diabetes
• Morbid obesity
• First-degree relative with diabetes mellitus
• Ethnic groups at higher risk:
• African
• Asian
• Hispanic
• Native American
• Pacific Islander
• History of impaired fasting glucose or impaired glucose tolerance
• History of low HDL cholesterol ( 35 mg/dL) or elevated triglycerides ( 250 mg/dL)
• Mothers with newborns of greater than 9 lbs
• Women with a history of gestational diabetes
• As an aid in the diagnosis of insulinoma
• To evaluate disorders of carbohydrate metabolism
• To detect hyperglycemia or hypoglycemia
• To monitor drug or diet therapy in patients with diabetes mellitus or metabolic syndrome
• Diabetes mellitus is a metabolic disorder characterized by hyperglycemia and abnormal protein, fat, and carbohydrate metabolism
• Type 1 Diabetes:
• Defect in insulin secretion
• Type 2 Diabetes:
• A defect in insulin action, or a combination of defects in secretion and action
• The American Diabetes Association’s (ADA) criteria for diagnosing Diabetes Mellitus include 3 possible methods to make the diagnosis:
• Any combination of the following findings or confirmation of any of the individual findings by repetition on a subsequent day:
• Symptoms of diabetes (e.g., polyuria, polydipsia, unexplained weight loss) in addition to a random glucose level 200-mg/dL (11.1 mmol/L).
• Fasting blood glucose 126 mg/dL (7.0 mmol/L), after a minimum of an 8-hour fast
• Glucose level 200 mg/dL (11.1 mmol/L) 2 hours after glucose challenge (GTT) with standardized 75 gram oral load of glucose

^* Note that any one of these items should be confirmed by repetition on a subsequent day; except in the case of unequivocal hyperglycemia. The Oral Glucose Challenge is not recommended routinely.
• The American Diabetes Association's (ADA) criteria for diagnosing "Impaired Glucose Tolerance" (IGT) or "Impaired Fasting Glucose" (IFG) include:
• Blood plasma glucose is 100-125 mg/dL or 5.6-6.9 mmol/L OR
• Glucose level 140 mg/dL (7.8 mmol/L) but 200 mg/dL (11.1 mmol/L) 2 hours after glucose challenge (GTT) with standardized 75 gram oral load of glucose

^* IGT or IFG, if left untreated, is high risk to develop into type 2 diabetes within 10 years.
• Glucose levels and vitamin deficiencies:
• Hyperglycemia may cause vitamin C deficiency by inhibiting cellular uptake of ascorbate. This is because of the structural similarity between glucose and vitamin C.

Additional information

• Interfering factors:
• Elevated urea levels (uremia) can lead to falsely elevated glucose levels
• Acetaminophen use can lead to falsely elevated test results when the testing technique is the glucose oxidase or hexokinase method
• Very high white blood cell counts can lead to falsely decreased glucose values
• Glycolysis due to failure to refrigerate sample or not sending it immediately to the laboratory may lead to falsely normal level
• Bacterial contamination of specimen
• Failure to separate clot from serum promptly
• Related laboratory tests include:
• Blood urea nitrogen
• C-Peptide
• Creatinine
• Fructosamine
• Glucose tolerance tests
• Glycated hemoglobin A_1c
• Insulin
• Ketones
• Microalbumin

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

^* Neonates with glucose 40-50 mg/dl (2.2-2.8 mmol/L) need to be carefully observed.

High Result

Conditions associated with elevated serum glucose levels (hyperglycemia) include:

• Type 1 or Type 2 Diabetes Mellitus
• Inability of pancreatic islet ß cells to produce adequate insulin
• Type 1 diabetes mellitus
• Pancreatitis:
• Acute
• Chronic
• Neoplasms of pancreas
• Defect in number or affinity of insulin receptors
• Type 2 diabetes mellitus
• Essential hypertension
• Ataxia telangiectasia
• Heavy smoking
• Parenteral glucose administration
• IV glucose - recent or current
• Total parenteral nutrition
• Inability of the liver to metabolize glycogen
• Advanced liver disease
• Hemochromatosis
• Chronic renal failure
• Altered levels of hormones that play a role in glucose metabolism
• Acromegaly
• Carcinoid syndrome
• Cushing's syndrome and disease
• Gigantism
• Glucagonoma
• Hypothalamic lesions
• Pheochromocytoma
• Pituitary adenoma
• Somatostatinoma
• Thyrotoxicosis
• Stress due to:
• Burns
• Cerebrovascular accident
• Convulsions
• Myocardial infarction
• Sepsis
• Shock
• Stroke
• Trauma
• Surgical procedures and anesthesia
• Others:
• Vitamin B deficiency - Wernicke's encephalopathy
• Pregnancy
• Obesity or sedentary lifestyle
• Non-fasting specimen
• Drugs and substances
• Acetazolamide
• Alanine
• Albuterol
• Anabolic steroids
• Anesthetic agents
• Antipyrine
• Benzothiadiazine diuretics
• Betamethasone
• Caffeine
• Cefotaxime
• Chlorpromazine
• Chlorprothixene
• Clofibrate
• Clonidine
• Clorexolone
• Corticotropin
• Cortisone
• Cyclic AMP
• Cyclopropane
• Dexamethasone
• Dextroamphetamine
• Diapamide
• Enflurane
• Epinephrine
• Estrogens
• Ethacrynic acid
• Ether
• Fludrocortisone
• Fluoxymesterone
• Furosemide
• Glucagon
• Glucocorticoids
• Glyburide
• Guanethidine
• Homoharringtonine
• Hydrochlorothiazide
• Hydroxydione
• Isoniazid
• Lisinopril
• Maltose
• MAO inhibitors
• Meperidine
• Meprednisone
• Metformin
• Methyclothiazide
• Metolazone
• Metoprolol
• Nandrolone
• Niacin
• Nifedipine
• Norepinephrine
• Norethindrone
• Nortriptyline
• Octreotide
• Oral contraceptives
• Oxyphenbutazone
• Pancreozymin
• Pargyline
• Phenelzine
• Phenylbutazone
• Phenytoin
• Piperacetazine
• Polythiazide
• Prazosin
• Prednisone
• Quinethazone
• Reserpine
• Rifampin
• Ritodrine
• Salbutamol
• Secretin
• Somatostatin
• Terazosin
• Thiazides
• Thyroid hormone
• Triamcinolone
• Troglitazone

Low Result

Conditions associated with decreased serum glucose levels (hypoglycemia) include:

• Insulinoma's (Pancreatic islet cell carcinoma, extrapancreatic stomach tumors)
• Endocrine hypofunctioning
• ACTH deficiency
• Addison's disease
• Anterior Pituitary adenoma
• Carcinoma of adrenal gland
• Hypopituitarism
• Hypothyroidism
• Liver damage
• Alcoholism
• Arsenic poisoning
• Chloroform poisoning
• Hepatic failure from any cause
• Enzyme-deficiency disorders
• Dormandy's syndrome
• Galactosemia
• Hereditary fructose intolerance
• Maple syrup disease
• Leucine sensitivity
• Von Gierke's syndrome
• Alimentary hyperinsulinism
• Gastrectomy
• Gastrojejunostomy
• Pyloroplasty
• Vagotomy
• Malaria Falciparum infection
• Erythroblastosis fetalis
• Stimulatory insulin-receptor antibodies
• Autoimmune insulin syndrome
• Premature infant
• Infant delivered to a mother with diabetes
• Starvation and malnutrition
• Intense exercise
• Factitious hypoglycemia:
• Insulin
• Oral hypoglycemic agents
• Artifactual hypoglycemia
• Bacterial contamination of specimen
• Failure to promptly separate clot from serum
• Leukocytosis
• Polycythemia vera
• Hematocrit >55%
• Drugs and substances
• Acarbose
• Acebutolol
• Acipimox
• Alanine
• Allopurinol
• Antimony compounds
• Arsenicals
• Ascorbic acid
• Benzene
• Buformin
• Calcitonin
• Cannabis
• Carbutamide
• Chloroform
• Chlorpromazine
• Chlorpropamide
• Chlorthalidone
• Clofibrate
• Danazol
• Dexfenfluramine
• Diazoxide
• Diethylstilbestrol
• Enprostil
• Ethacrynic acid
• Ethanol
• Exenatide
• Fenfluramine
• Foscarnet
• Gemfibrozil
• Glimepiride
• Glipizide
• Glyburide
• Haloperidol
• Imipramine
• Insulin
• Interferon -2A
• Lithium
• Mestranol
• Metformin
• Miglitol
• Nateglinide
• Niacin
• Niceritrol
• Nicotinic acid
• Octreotide
• Oxandrolone
• Oxymetholone
• Perphenazine
• Pioglitazone
• Phentolamine
• Phosphorus
• Pramlintide
• Promethazine
• Repaglinide
• Rosiglitazone
• Sitagliptin
• Sulfonylureas
• Tolbutamide

Conditions associated with neonatal hypoglycemia, include:

• Inadequate feeding
• Underlying infection/sepsis
• Mother with diabetes
• Adenomatous islet cell hyperplasia
• Beckwith syndrome
• Carnitine deficiency - Reye's syndrome
• Diffuse Beta-cell hyperplasia
• Familial persistent hyperinsulinemic hypoglycemia of infancy
• Galactosemia
• Glucokinase mutations
• Glutamate dehydrogenase enzyme deficiency
• Glycogen storage diseases
• Hereditary fructose intolerance
• Hyperinsulinism and hyperammonemia
• Ketogenic hypoglycemia of infancy
• Mutation of Beta-cell sulfonylurea receptor (SURI) genes
• Mutations in glukokinase

References

• Diagnosis and Classification of Diabetes Mellitus. American Diabetes Association (Position Statement). Diabetes Care 2006;29:S43-48.
• Khan HA et al. Fluctuations in fasting blood glucose and serum fructosamine in pregnant women monitored on successive antenatal visits. Clin Exp Med. 2006 Oct; 6(3): 134-7.
• Kovatchev BP et al. Evaluation of a new measure of blood glucose variability in diabetes. Diabetes Care. 2006 Nov; 29(11): 2433-8.
• LabTestsOnline®. Glucose. [Homepage on the Internet]© 2001-2006. Last reviewed on March 23, 2005. Last accessed on October 31, 2006. Available at URL: http://www.labtestsonline.org/understanding/analytes/glucose/sample.html
• Lidfeldt J et al. Obese women and the relation between cardiovascular risk profile and hormone therapy, glucose tolerance, and psychosocial conditions. Diabetes Care. 2006 Nov; 29(11): 2477-82.
• Price KD et al. Hyperglycemia-induced ascorbic acid deficiency promotes endothelial dysfunction and the development of atherosclerosis. Atherosclerosis. 2001 Sep;158(1):1-12
• Shi D et al. [Blood lipids and glucose levels in patients with periodontitis. Zhonghua Kou Qiang Yi Xue Za Zhi. 2006 Jul; 41(7): 401-2.
• Suvarna J et al. Insulin resistance and beta cell function in chronically transfused patients of thalassemia major. Indian Pediatr. 2006 May; 43(5): 393-400.
• The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 1997;20:1183-1197.
• The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Follow-up report on the diagnosis of diabetes mellitus. Diabetes Care 2003;26:3160-3167.
• UTMB Laboratory Survival Guide®. GLUCOSE, serum, plasma, or whole blood. [Homepage on the Internet]© 2006. Last reviewed on February, 2006. Last accessed on November 21, 2006. Available at URL: http://www.utmb.edu/lsg/LabSurvivalGuide/chem/GLUCOSEserum_whole.html