Blood glucose (serum glucose, plasma glucose) is measured in a variety of situations. In the fasting state, the serum glucose level gives the best indication of overall glucose homeostasis.6
Blood glucose levels also can be measured at regular intervals throughout the day to monitor responses to diet and medications in persons with a diagnosis of abnormalities of glucose metabolism. Such monitoring may take place in a hospital setting or in the home with kits specially designed for self-monitoring of blood glucose. Serial blood glucose levels also are used to determine insulin requirements in clients with uncontrolled diabetes mellitus and for individuals receiving total parenteral or enteral nutritional support.
In addition to situations characterized by actual or potential elevations in blood sugar, glucose levels are evaluated in individuals suspected or known to have hypoglycemia.
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Newborns
| Conventional Units | SI Units |
|---|
| Whole blood | 25-51 mg/dL | 1.4-2.8 mmol/L |
| Serum/plasma | 30-60 mg/dL | 1.7-3.3 mmol/L |
| Critical values | <30 mg/dL or >300 mg/dL | <1.6 mmol/L or >16.5 mmol/L |
Children
| Conventional Units | SI Units |
|---|
| Whole blood | 50-90 mg/dL | 2.8-5.0 mmol/L |
| Serum/plasma | 60-105 mg/dL | 3.3-5.8 mmol/L |
| Critical values | <40 mg/dL or >700 mg/dL | <2.2 mmol/L or >38.6 mmol/L |
Adults
| Conventional Units | SI Units |
|---|
| Whole blood | 60-100 mg/dL | 3.3-5.6 mmol/L |
| Serum/plasma | 70-110 mg/dL | 3.9-6.1 mmol/L |
| Critical values | <40 mg/dL or >700 mg/dL | <2.2 mmol/L or >38.6 mmol/L |
Note: Values may vary depending on the laboratory method used.
[Table Outline]
Nursing Care Before the Procedure
Client preparation is essentially the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).
- If a fasting sample is to be drawn, food and insulin or any oral hypoglycemic agent should be withheld for approximately 8 hours before the test (i.e., the client usually takes only water from midnight until the sample is drawn in the morning).
- For home glucose monitoring, the client should be instructed in the correct use of the testing equipment and in the method used to obtain the blood sample.
A venipuncture is performed and the sample is obtained in either a gray- or a red-topped tube, depending on the laboratory performing the test. The sample should be handled gently to avoid hemolysis and transported promptly to the laboratory.
A capillary sample may be obtained in infants and children as well as in adults for whom venipuncture may not be feasible. Capillary samples also are used for self-monitoring of blood glucose.
Nursing Care After the Procedure
Care and assessment after the procedure are the same as for any study involving collection of a peripheral blood sample.
- Resume food and medications withheld before the test after the sample is drawn.
- Abnormal values: Note and report increased levels. Assess for symptoms associated with hyperglycemia such as polyuria and possible dehydration, polydipsia, or weight loss. Prepare for additional glucose tests for diabetes mellitus. Monitor intake and output (I&O). Prepare to administer ordered medications (insulin or oral hypoglycemic) to treat known diabetic condition. Instruct client on diabetic diet in relation to medications, activities, and blood and urine test results. Note and report decreased levels. Assess for symptoms associated with hypoglycemia such as weakness, sweating, nervousness, hunger, confusion, or palpitations. Prepare to administer sucrose or glucose orally or intravenously (IV). Instruct client to keep readily absorbed carbohydrates on hand. Instruct client on diet and its relation to medications, activities, and blood and urine test results.
- Critical values: Notify the physician immediately of a blood glucose level of less than 30 mg/dL in infants or less than 40 mg/dL in adults or a blood glucose level of greater than 300 mg/dL in infants or greater than 700 mg/dL in adults.