Quick facts
| Test | Range | Unit | Applies to |
|---|---|---|---|
| Glucose (UW reference range)[1] | 62-125 | mg/dL | All ages; a fasting 126 or higher is diabetes |
| Fasting plasma glucose, normal[2] | 99 or below | mg/dL | Diagnosis cutoff |
| Fasting plasma glucose, diabetes[1][2] | 126 or higher | mg/dL | Diagnosis cutoff |
| Random plasma glucose, diabetes[2] | 200 or higher | mg/dL | With symptoms of diabetes |
| Hypoglycemia[3] | Below 70 | mg/dL | Hypoglycemia threshold |
The lab range and the diagnosis cutoffs are different numbers
- UW's range runs from 62 to 125 mg/dL, and its upper limit comes from the fasting cutoff for diabetes. A fasting result of 100 to 125 sits inside that range but is prediabetes, and a result of 62 to 69 is inside it but below the 70 mg/dL hypoglycemia threshold.[1][2][3]
- A fasting glucose is drawn after at least 8 hours without food or drink other than water. A random glucose can be drawn at any time, even after eating, and a second test usually confirms diabetes.[2][5]
Below 70 mg/dL is hypoglycemia, and insulin raises the risk
- Hypoglycemia is a blood glucose below 70 mg/dL, and patients on insulin are at risk. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes severe hypoglycemia as glucose so low the patient can't treat it on their own.[3][6]
- Mild to moderate signs include shakiness, sweating, hunger, headache, and a fast heartbeat. Left untreated, very low glucose can cause seizures and brain damage.[3][5][6]
- Beta blockers such as metoprolol can mask the signs of hypoglycemia, so glucose is monitored closely in patients with diabetes who take them.[7]
- When glucose is below 70 mg/dL, NIDDK teaches people with diabetes who can treat a low themselves to have 15 to 20 grams of glucose or carbohydrate, then recheck in 15 minutes.[6]
The Glucose care: clinical reasoning flashcard deck covers hypoglycemia, diabetic ketoacidosis, and hyperosmolar hyperglycemic state. Find the deck in the free app preview.
Open the free app previewHow it shows up on nursing exams
Practice question
A nurse checks capillary blood glucose before breakfast for four adult patients with diabetes. Which result should the nurse act on first?
- A. Takes insulin and metoprolol: glucose 96 mg/dL, no symptoms
- B. Takes insulin: glucose 64 mg/dL, says they feel shaky
- C. Takes an oral diabetes medicine: glucose 128 mg/dL
- D. Manages diabetes with diet: glucose 112 mg/dL
Show the answer and why
Correct answer: B. Takes insulin: glucose 64 mg/dL, says they feel shaky
- A. Incorrect. Metoprolol can mask the signs of hypoglycemia, which is why glucose is monitored closely, but 96 mg/dL is not low.
- B. Correct. 64 mg/dL is below 70, which is hypoglycemia, and shakiness is a mild-to-moderate sign. Patients on insulin are at risk. Act on this result first: treat the low glucose and recheck it in 15 minutes.
- C. Incorrect. 128 mg/dL is not low, so it is less urgent than a glucose below 70 mg/dL.
- D. Incorrect. 112 mg/dL is above 70 and needs no immediate action.
Sources for this question: [2][3][6][7]
Memory hook: Three glucose numbers: below 70 is low, 100 to 125 fasting is prediabetes, 126 or higher fasting is diabetes.