Should blood sugar be checked in patients with diabetes or at risk for hyperglycemia (high blood sugar) or hypoglycemia (low blood sugar)?

Should Blood Sugar Be Checked?

Yes, blood sugar should be checked in all patients with diabetes or at risk for hyperglycemia or hypoglycemia, with the frequency and timing determined by their specific treatment regimen and clinical context. 1

Who Requires Blood Glucose Monitoring

Mandatory Screening Populations

• All patients with known diabetes should have blood glucose monitored, regardless of setting (hospital, correctional facility, or outpatient) 1
• All patients presenting with acute coronary syndromes require glycemic status evaluation on hospital admission, even without a diabetes history 1
• Patients on insulin therapy (including basal-only regimens) must check blood glucose at least 4 times daily: before breakfast, before dinner, at bedtime, and when suspecting hypoglycemia 2
• Critically ill or hospitalized patients should have blood glucose assessed to identify hyperglycemia (>180 mg/dL) or hypoglycemia 1
• Patients with altered mental status, agitation, or diaphoresis require immediate fingerstick glucose testing, as these symptoms can mimic intoxication but may represent severe hypoglycemia 1

High-Risk Situations Requiring Immediate Testing

• Patients taking insulin, sulfonylureas, or meglitinides are at significant risk for hypoglycemia and require regular monitoring 1
• Correctional facility intake: All insulin-treated patients must have capillary blood glucose checked within 1-2 hours of arrival 1
• Before and after exercise to prevent exercise-induced hypoglycemia 2
• Before critical tasks such as driving to ensure safety 1, 2
• During acute illness or stress, as insulin requirements change with intercurrent conditions 3

Monitoring Frequency by Treatment Type

Intensive Insulin Regimens (Multiple Daily Injections or Pump)

• Check glucose 6-10 times daily: before all meals and snacks, at bedtime, occasionally postprandially, before exercise, when suspecting low glucose, after treating hypoglycemia until normoglycemic, and before critical tasks 1
• Never skip bedtime testing with premixed insulins like 70/30 due to overnight NPH action and nocturnal hypoglycemia risk 2

Basal Insulin Only

• At minimum, assess fasting glucose to guide dose adjustments toward target blood glucose 1
• Frequency should be individualized but less intensive than multiple daily injection regimens 1

Oral Agents Without Hypoglycemia Risk

• Routine monitoring may be of limited benefit, but consider checking when altering diet, physical activity, or medications as part of a treatment adjustment program 1

Hospitalized Patients

• Frequency depends on diabetes treatment method (insulin vs. oral agents), effect of hyperglycemia on the clinical condition, and overall patient stability 1
• Target blood glucose <180 mg/dL while avoiding hypoglycemia 1
• In critically ill patients, use arterial blood gas analyzers rather than capillary glucometers, as point-of-care capillary testing can be inaccurate in shock states or with vasopressor use 1

Critical Clinical Scenarios

Hypoglycemia Recognition and Response

• Level 1 hypoglycemia: Glucose 54-70 mg/dL requires treatment with 15-20g oral glucose 1
• Level 2 hypoglycemia: Glucose <54 mg/dL is clinically significant and requires immediate treatment 1
• Level 3 hypoglycemia: Severe hypoglycemia with altered mental status requires glucagon (1 mg IM/SC for adults) or IV dextrose 4
• Recheck glucose 15 minutes after treatment and repeat until normoglycemic (≥70 mg/dL) 1

Hyperglycemia Thresholds

• Hospital setting: Initiate glucose-lowering therapy when blood glucose >180 mg/dL 1
• Acute coronary syndrome: Consider treatment when glucose >10 mmol/L (>180 mg/dL), with targets adapted to comorbidities 1
• Avoid intensive insulin therapy (targeting 80-110 mg/dL) in critically ill patients due to increased hypoglycemia risk and no mortality benefit 1

Special Populations

Patients at High Risk for Hypoglycemia

Screen at least yearly for impaired hypoglycemia awareness using validated questionnaires (Clark or Gold scores) or by asking if patients experience low glucose without symptoms 1

Major risk factors include:

• Prior level 2 or 3 hypoglycemic events 1
• Long-standing diabetes with impaired counterregulatory hormone release 1
• Older age, multimorbidity, cognitive impairment 1
• Chronic kidney disease or end-stage renal disease 1
• Female sex (independent risk factor) 1

Patients Starting Levothyroxine

• Monitor blood glucose closely during the first 3-4 weeks after initiation and after dose adjustments 5
• Consider reducing insulin dose by approximately 20% and sulfonylurea/glinide dose by 50% when starting levothyroxine 5

Pregnant Patients

• High-risk women should undergo glucose testing as soon as possible at first prenatal visit 1
• Average-risk women should be tested between 24-28 weeks gestation 1

Common Pitfalls to Avoid

• Do not rely on symptoms alone: Hypoglycemia awareness may be impaired in patients with long-standing diabetes, and symptoms can be masked by beta-blockers 1, 3
• Do not use capillary glucometers in critically ill patients: Results are inaccurate in shock states; use arterial blood gas analyzers instead 1
• Do not use sliding-scale insulin alone in hospitalized patients: Basal-bolus regimens produce better outcomes 1
• Do not diagnose diabetes during acute illness: Hyperglycemia during NSTEMI may be stress-related; confirm diagnosis after hospital discharge 1
• Do not forget to replace expired glucagon: All insulin-treated patients should have unexpired glucagon available 4