Blood sugar, fasting blood sugar (FBS), postprandial glucose, 2-hr PC (post cibum).
To assist in the diagnosis of diabetes and to evaluate disorders of carbohydrate metabolism such as malabsorption syndrome.
Serum collected in a gold-, red-, or red/gray-top tube, although plasma is recommended for diagnosis of diabetes. Plasma collected in a gray-top (sodium fluoride) or a green-top (heparin) tube.
|Age||Conventional Units||SI Units (Conventional Units × 0.0555)|
|Cord blood||45–96 mg/dL||2.5–5.3 mmol/L|
|Premature infant||20–80 mg/dL||1.1–4.4 mmol/L|
|Newborn 2 d–2 yr||30–100 mg/dL||1.7–5.6 mmol/L|
|Child||60–100 mg/dL||3.3–5.6 mmol/L|
|Adult-older adult||Less than 100 mg/dL||Less than 5.6 mmol/L|
|Prediabetes or impaired fasting glucose||100–125 mg/dL||5.6–6.9 mmol/L|
|2-hr postprandial||65–139 mg/dL||3.6–7.7 mmol/L|
|Prediabetes or impaired 2-hr sample||140–199 mg/dL||7.8–11 mmol/L|
|Random||Less than 200 mg/dL||Less than 11.1 mmol/L|
|The American Diabetes Association and National Institute of Diabetes and Digestive and Kidney Diseases consider a confirmed fasting blood glucose greater than 126 mg/dL to be consistent with a diagnosis of diabetes. Values tend to increase in older adults.|
DescriptionGlucose, a simple six-carbon sugar (monosaccharide), enters the diet as part of the sugars sucrose, lactose, and maltose and from the complex polysaccharide, dietary starch. The body acquires most of its energy from the oxidative metabolism of glucose. Excess glucose is stored in the liver or in muscle tissue as glycogen. Glucose levels in plasma (one of the components of blood) are generally 10% to 15% higher than glucose measurements in whole blood (and even more after eating). This is important because home blood glucose meters measure the glucose in whole blood, whereas most laboratory tests measure the glucose in either plasma or serum.
Diabetes is a group of diseases characterized by hyperglycemia, or elevated glucose levels. Hyperglycemia results from a defect in insulin secretion due to destruction of the beta cells of the pancreas (type 1 diabetes), a defect in insulin action, or a combination of defects in secretion and action (type 2 diabetes). The chronic hyperglycemia of diabetes over time may lead to damage, dysfunction, and eventually failure of the eyes (retinopathy), kidneys (nephropathy), nerves (neuropathy), heart (cardiovascular disease), and blood vessels (microvascular and macrovascular conditions). The American Diabetes Association (ADA) and National Institute of Diabetes and Digestive and Kidney Disease have established criteria for diagnosing diabetes to include any combination of the following findings or confirmation of any of the individual findings by repetition of the same test on a subsequent day:
- Symptoms of diabetes (e.g., polyuria, polydipsia, polyphagia, unexplained weight loss) in addition to a random glucose level greater than 200 mg/dL (SI: 11.1 mmol/L)
- Fasting blood glucose greater than 126 mg/dL (SI: 7 mmol/L) after fasting for a minimum of 8 hr
- Glucose level greater than 200 mg/dL (SI: 11.1 mmol/L) 2 hr after glucose challenge with standardized 75-mg load
- An A1C(glycated hemoglobin) in adults equal to or greater than 6.5% (assumes the use of a standardized test as referenced to the National Glycohemoglobin Standardization Program—Diabetes Control and Complications Trial and the absence of clinical conditions such as hemoglobinopathies, anemias, and kidney and liver diseases known to affect the accuracy of the test results)
|1,5–Anhydroglucitol Measured Using the GlycoMark Assay||Hemoglobin A1c||Estimated Blood Glucose (mg/dL)||Degree of Diabetic Control|
|14 mcg/mL or greater||4%–5%||68–97 mg/dL||Normal/nondiabetic|
|10–12 mcg/mL||4%–6%||68–126 mg/dL||Well controlled|
|5–10 mcg/mL||6%–8%||126–183 mg/dL||Moderately well controlled|
|2–5 mcg/mL||8%–10%||183–240 mg/dL||Poorly controlled|
|Less than 2 mcg/mL||Greater than 10% (11%–14%)||269–355 mg/dL||Very poorly controlled|
Assessment of medications used to manage diabetes is an important facet of controlling the disease and its health-related complications. Drug response is an active area of study to ensure that the medications prescribed are meeting the needs of the patients who are taking them. Insulin and metformin are two commonly prescribed medications for the treatment of diabetes. See the “Insulin Antibodies” study for more detailed information. The AccuType Metformin Assay is a genetic test that identifies individuals who may not respond appropriately or who have a suboptimal response to metformin related to a genetic mutation in the proteins responsible for transporting metformin.
This procedure is contraindicated forN/A
- Assist in the diagnosis of insulinoma.
- Determine insulin requirements.
- Evaluate disorders of carbohydrate metabolism.
- Identify hypoglycemia.
- Screen for diabetes.
- Acromegaly, gigantism (growth hormone [GH] stimulates the release of glucagon, which in turn increases glucose levels)
- Acute stress reaction (hyperglycemia is stimulated by the release of catecholamines and glucagon)
- Cerebrovascular accident (possibly related to stress)
- Chronic kidney disease (glucagon is degraded by the kidneys; when damaged kidneys cannot metabolize glucagon, glucagon levels in blood rise and result in hyperglycemia)
- Cushing’s syndrome (related to elevated cortisol)
- Diabetes (glucose intolerance and elevated glucose levels define diabetes)
- Glucagonoma (glucagon releases stored glucose; glucagon-secreting tumors will increase glucose levels)
- Hemochromatosis (related to iron deposition in the pancreas; subsequent damage to pancreatic tissue releases cell contents, including glucagon, resulting in hyperglycemia)
- Liver disease (severe) (damaged liver tissue releases cell contents, including stored glucose, into circulation)
- Metabolic syndrome (related to the development of diabetes)
- Myocardial infarction (related to stress and/or preexisting diabetes)
- Pancreatic adenoma (damage to pancreatic tissue releases cell contents, including glucagon, resulting in hyperglycemia)
- Pancreatitis (acute and chronic) (damage to pancreatic tissue releases cell contents, including glucagon, resulting in hyperglycemia)
- Pancreatitis due to mumps (damage to pancreatic tissue releases cell contents, including glucagon, resulting in hyperglycemia)
- Pheochromocytoma (related to increased catecholamines, which increase glucagon; glucagon increases glucose levels)
- Shock, trauma (hyperglycemia is stimulated by the release of catecholamines and glucagon)
- Somatostatinoma (somatostatin-producing tumor of pancreatic delta cells, associated with diabetes)
- Strenuous exercise (hyperglycemia is stimulated by the release of catecholamines and glucagon)
- Thyrotoxicosis (related to loss of kidney function)
- Vitamin B1 deficiency (thiamine is involved in the metabolism of glucose; deficiency results in accumulation of glucose)
- Acute alcohol ingestion (most glucose metabolism occurs in the liver; alcohol inhibits the liver from making glucose)
- Addison’s disease (cortisol affects glucose levels; insufficient levels of cortisol result in diminished glucose levels)
- Ectopic insulin production from tumors (adrenal carcinoma, carcinoma of the stomach, fibrosarcoma)
- Excess insulin by injection
- Galactosemia (inherited enzyme disorder that results in accumulation of galactose in excessive proportion to glucose levels)
- Glucagon deficiency (glucagon controls glucose levels; hypoglycemia occurs in the absence of glucagon)
- Glycogen storage diseases (deficiencies in enzymes involved in conversion of glycogen to glucose)
- Hereditary fructose intolerance (inherited disorder of fructose metabolism; phosphates needed for intermediate steps in gluconeogenesis are trapped from further action by the enzyme deficiency responsible for fructose metabolism)
- Hypopituitarism (decreased levels of hormones such as adrenocorticotropic hormone [ACTH] and GH result in decreased glucose levels)
- Hypothyroidism (thyroid hormones affect glucose levels; decreased thyroid hormone levels result in decreased glucose levels)
- Insulinoma (the function of insulin is to decrease glucose levels)
- Malabsorption syndromes (insufficient absorption of carbohydrates)
- Maple syrup urine disease (inborn error of amino acid metabolism; accumulation of leucine is believed to inhibit the rate of gluconeogenesis, independently of insulin, and thereby diminish release of hepatic glucose stores)
- Poisoning resulting in severe liver disease (decreased liver function correlates with decreased glucose metabolism)
- Postgastrectomy (insufficient intake of carbohydrates)
- Starvation (insufficient intake of carbohydrates)
- von Gierke’s disease (most common glycogen storage disease; G6PD deficiency)
Adults & children
- Less than 40 mg/dL (SI: Less than 2.22 mmol/L)
- Greater than 400 mg/dL (SI: Greater than 22.2 mmol/L)
- Less than 32 mg/dL (SI: Less than 1.8 mmol/L)
- Greater than 328 mg/dL (SI: Greater than 18.2 mmol/L)
Note and immediately report to the requesting health-care provider (HCP) any critical findings and related symptoms. A listing of these findings varies among facilities. Timely notification of a critical finding for laboratory or diagnostic studies is a role expectation of the professional nurse. The notification processes vary among facilities. Upon receipt of the critical finding, the information should be read back to the caller to verify accuracy.
Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.
Glucose monitoring is an important measure in achieving tight glycemic control. The enzymatic GDH-PQQ test method may produce falsely elevated results in patients who are receiving products that contain other sugars (e.g., oral xylose, parenterals containing maltose or galactose, and peritoneal dialysis solutions that contain icodextrin). The GDH-NAD, glucose oxidase, and glucose hexokinase methods can distinguish between glucose and other sugars.
Symptoms of decreased glucose levels include headache, confusion, polyphagia, irritability, nervousness, restlessness, diaphoresis, and weakness. Possible interventions include oral or intravenous (IV) administration of glucose, IV or intramuscular injection of glucagon, and continuous glucose monitoring.
Symptoms of elevated glucose levels include abdominal pain, fatigue, muscle cramps, nausea, vomiting, polyuria, polyphagia, and polydipsia. Possible interventions include fluid replacement in addition to subcutaneous or IV injection of insulin with continuous glucose monitoring.
- Drugs and other substances that may increase glucose levels include acetazolamide, alanine, albuterol, anesthetic drugs, antipyrine, atenolol, betamethasone, cefotaxime, chlorpromazine, chlorprothixene, clonidine, clorexolone, corticotropin, cortisone, cyclic AMP, cyclopropane, dexamethasone, dextroamphetamine, diapamide, epinephrine, enflurane, ethacrynic acid, ether, fludrocortisone, furosemide, glucagon, glucocorticoids, homoharringtonine, hydrochlorothiazide, hydroxydione, isoniazid, maltose, meperidine, meprednisone, methyclothiazide, metolazone, niacin, nifedipine, nortriptyline, octreotide, oral contraceptives, oxyphenbutazone, pancreozymin, phenelzine, phenylbutazone, piperacetazine, polythiazide, prednisone, quinethazone, reserpine, rifampin, ritodrine, secretin, somatostatin, thiazides, thyroid hormone, and triamcinolone
- Drugs and other substances that may decrease glucose levels include acarbose, acetylsalicylic acid, acipimox, alanine, allopurinol, antimony compounds, arsenicals, ascorbic acid, benzene, buformin, cannabis, captopril, chloroform, clofibrate, enalapril, enprostil, erythromycin, gemfibrozil, glibornuride, glyburide, guanethidine, niceritrol, nitrazepam, oral contraceptives, phentolamine, phosphorus, promethazine, ramipril, rotenone, sulfonylureas, thiocarlide, tolbutamide, tromethamine, and verapamil
- Elevated urea levels and uremia can lead to falsely elevated glucose levels.
- Extremely elevated white blood cell counts can lead to falsely decreased glucose values.
- Administration of insulin or oral hypoglycemic drugs within 8 hr of a fasting blood glucose can lead to falsely decreased values.
- Specimens should never be collected above an IV line because of the potential for dilution when the specimen and the IV solution combine in the collection container, falsely decreasing the result. There is also the potential of contaminating the sample with the substance of interest, if it is present in the IV solution, falsely increasing the result.
- Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated; failure to follow dietary restrictions before the fasting test can lead to falsely elevated glucose values.
Nursing Implications Procedure
- Related tests include ACTH, angiography adrenal, BUN, calcium, catecholamines, cholesterol (HDL, LDL, total), cortisol, C-peptide, CT cardiac scoring, CRP, CK and isoenzymes, creatinine, DHEA, echocardiography, fecal analysis, fecal fat, fluorescein angiography, fructosamine, fundoscopy, gastric emptying scan, glucagon, GTT, glycated hemoglobin, gonioscopy, Holter monitor, HVA, insulin, insulin antibodies, ketones, lactic acid, lipoprotein electrophoresis, MRI chest, metanephrines, microalbumin, myoglobin, MI infarct scan, myocardial perfusion heart scan, plethysmography, PET heart, renin, sodium, troponin, and visual fields test.
- Refer to the Endocrine System Table for related test by body system.
Potential Nursing Problems
|Problem||Signs & Symptoms||Interventions|
|Blood glucose (related to sedentary lifestyle, circulating insulin deficiency secondary to pancreatic insufficiency; excessive dietary intake; insulin resistance)||Excess: Fatigue; mild dehydration; elevated blood glucose; weight loss; weakness; polyuria; polydipsia; polyphagia; blurred vision; headache; paresthesia; poor skin turgor; dry mouth; nausea; vomiting; abdominal pain; Kussmaul respirations. Deficit: Tremor, diaphoresis, decreased concentration; diaphoresis; elevated blood pressure; palpitations; headache; polyphagia; restlessness; lethargy; altered mental status; combativeness; altered speech; altered coordination||Check blood glucose before meals and at bedtime; administer prescribed insulin or oral drugs; educate and encourage the patient to participate in glucose self-check and record results; assess readiness to learn and barriers to learning; collaborate with the HCP and dietitian to support medical nutritional therapy; refer to dietitian to assist the patient to select appropriate cultural foods; develop a plan of exercise commensurate with the patient’s physical abilities; discuss lifestyle alterations necessary to support positive health management secondary to disease process; teach good hygiene and infection prevention; monitor laboratory studies that may be impacted by altered glucose and trend results (Hgb A1C; BUN; creatinine; electrolytes; arterial pH; magnesium; urine ketones; urine microalbumin; white blood cell [WBC] count; amylase; Hgb/Hct; C-reactive protein; liver enzymes); facilitate oral hydration; correlate blood glucose with other laboratory values and medical conditions; address the psychosocial aspects of the disease; monitor serum insulin levels|
|Infection risk (related to altered blood glucose; exposure to opportunistic hosts; poor personal hygiene; broken skin; wound presence)||Increased temperature; increased heart rate and respiratory rate; chills; change in mental status; fatigue; malaise; weakness; anorexia; headache; nausea; elevated blood glucose; hypotension; diminished oxygen saturation; elevated WBC; elevated C-reactive protein||Provide standard precautions in the provision of care; correlate symptoms with laboratory values and disease process; trend vital signs and laboratory values to monitor for improvement; administer prescribed antibiotics and medications for fever reduction; provide cooling measures; ensure vigilant hand hygiene; educate patient and family regarding good hand hygiene; infuse ordered IV fluids to support adequate hydration; ensure implementation of infection prevention measures with consideration of age and culture such as adequate nutrition; provide aseptic wound care; ensure good skin care; ensure good oral care; ensure adequate rest; instruct patient to avoid exposure to opportunistic hosts; send cultures to the laboratory as ordered; correlate culture findings with selected antibiotics|
|Noncompliance (related to refusal to accept new diagnosis; financial instability; cultural norms; complexity of the medical management; lack of knowledge)||Insufficient disease management; alterations in blood glucose; poor self-management of medication administration; lack of supplies to support self-management; poor dietary control with inappropriate food selections||Assess the patient’s ability to and prior efforts to manage the disease process; evaluate the ability to self-manage the disease, including blood glucose screening, dietary management, exercise, and medication self-administration; assess for personal factors that may limit the patient’s ability to self-perform, such as visual, cognitive, and hearing; assess the financial ability to purchase the medication and supplies necessary to provide self-care; assess the level of family support; ensure the patient has the adequate knowledge to perform self-care, and if not, provide the necessary training; ensure the patient knows the signs and symptoms related to the disease process; teach correct dietary selections meeting cultural- and age-appropriate needs; refer to social services or home health care; discuss how to manage diabetes during travel|
|Nutrition (related to excessive dietary intake more than body requirements, insulin deficiency, stress; anxiety; depression; cultural lifestyle; unhealthy food sources; financial restrictions)||Polydipsia, polyuria, weight loss; fatigue; elevated blood glucose levels; inadequate glucose management; polyphagia||Monitor blood glucose results, refer to dietitian for evaluation, administer insulin or oral antihyperglycemic drug; assess the cultural aspects of diet selection; correlate dietary intake with blood glucose and monitor trends; collaborate with a dietitian to develop a cultural- and age-appropriate diet plan; correlate nutritional intake and exercise; ensure that the patient understands the relationship between caloric intake and medication (insulin, oral drug); refer to social services and dietitian as necessary|
- Positively identify the patient using at least two person-specific identifiers before services, treatments, or procedures are performed.
- Patient Teaching: Inform the patient this test can assist in evaluating blood sugar levels.
- Obtain a history of the patient’s health concerns, symptoms, surgical procedures, and results of previously performed laboratory and diagnostic studies. Include a list of known allergens, especially allergies or sensitivities to latex.
- Obtain a list of the patient’s current medications, including over-the-counter medications and dietary supplements (see Effects of Dietary Supplements online at DavisPlus).
- Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
- Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
- Instruct the patient to fast for at least 8 hr before specimen collection and not to consume any caffeinated products or chew any type of gum before specimen collection for the fasting glucose test; these factors are known to elevate glucose levels.
- Instruct the patient to follow the instructions given for 2-hr postprandial glucose test. Some HCPs may order administration of a standard glucose solution, whereas others may instruct the patient to eat a meal with a known carbohydrate composition.
- Ensure that the patient has complied with dietary restrictions and other pretesting preparations prior to the fasting study, as instructed.
- Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
- Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
- Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection online at DavisPlus. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
- Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
- Promptly transport the specimen to the laboratory for processing and analysis.
- Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
- Instruct the patient to resume usual diet, as directed by the HCP.
- Nutritional Considerations: Increased glucose levels may be associated with diabetes. There is no “diabetic diet”; however, many meal-planning approaches with nutritional goals are endorsed by the ADA Patients who adhere to dietary recommendations report a better general feeling of health, better weight management, greater control of glucose and lipid values, and improved use of insulin. Instruct the patient, as appropriate, in nutritional management of diabetes. A variety of dietary patterns are beneficial for people with diabetes. The Mediterranean-style diet emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed) along with fish and lean poultry. A similar dietary pattern known as the Dietary Approaches to Stop Hypertension (DASH) diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium. A vegetarian diet as well as other potential weight loss diets such as Weight Watchers are also supported by the ADA If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The nutritional needs of each patient with diabetic patient need to be determined individually (especially during pregnancy) with the appropriate HCPs, particularly professionals educated in nutrition.
- Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population aged 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the pediatric patient and caregiver regarding health risks and weight control education.
- Social and Cultural Considerations: Studies comparing risk for developing diabetes demonstrate that certain populations are disproportionately affected by type 2 diabetes and complications of type 2 diabetes as compared to the general population. Nonmodifiable risk factors include age, ethnicity, and family history of diabetes or metabolic syndrome. The risk of developing type 2 diabetes increases with age. In the United States, affected populations include African Americans, Asian Americans, Hispanics, native Hawaiians and Pacific Islanders, American Indians, and Alaska natives. Modifiable risk factors include lifestyle choices related to making healthy dietary choices, maintaining a healthy body weight, and meeting recommended levels of physical activity. The financial and emotional burdens of diabetes and related complications continue to grow at an alarming rate. A system for the prevention, management, and support of patients with type 2 diabetes should be provided through the coordinated efforts of multidisciplinary partners using strategies that are culturally appropriate.
- Recognize anxiety related to test results, and be supportive of perceived loss of independence and fear of shortened life expectancy. The ADA recommends A1C testing four times a year for insulin-dependent type 1 or type 2 diabetes when glycemic targets are not being met or when therapy has changed and twice a year when treatment goals are being met for non–insulin-dependent type 2 diabetes. The ADA also recommends that testing for diabetes commence at age 45 for asymptomatic individuals, be considered for adults of any age who are overweight and have additional risk factors, and continue every 3 yr in the absence of symptoms.
- Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
- Instruct the patient and caregiver to report signs and symptoms of hypoglycemia (weakness, confusion, diaphoresis, rapid pulse) or hyperglycemia (thirst, polyuria, hunger, lethargy).
- Discuss the implications of abnormal test results on the patient’s lifestyle.
- Provide teaching and information regarding the clinical implications of the test results, as appropriate.
- Emphasize, if indicated, that good glycemic management delays the onset and slows the progression of diabetic retinopathy, nephropathy, and neuropathy.
- Educate the patient regarding access to counseling services, as appropriate.
- Provide contact information, if desired, for the American Heart Association (www.americanheart.org), National Heart, Lung, and Blood Institute (www.nhlbi.nih.gov), Institute of Medicine of the National Academies (www.iom.edu), and USDA’s resource for nutrition (www.choosemyplate.gov).
- Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
- Instruct the patient in the use of home testing strips or meters approved for glucose, ketones, or A1C by the U.S. Food and Drug Administration, if prescribed.
- Answer any questions or address any concerns voiced by the patient or family.
- Teach the patient and family the signs and symptoms of hyperglycemia and hypoglycemia.
Expected Patient Outcomes:
- The patient and family state the signs and symptoms that could indicate an infection because of the risk for developing ulcers or the potential for limb amputation.
- The patient and family state the value of good glucose management to their overall health and longevity.
- The patient demonstrates proficiency in the ability to perform accurate self-monitored glucose checks.
- The patient demonstrates proficiency in the ability to perform insulin self-administration correctly or to take oral antihyperglycemic drugs.
- The patient complies with the medication management recommended by the HCP.
- The patient complies with dietary restrictions.
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