What are the recommended fasting blood‑glucose targets for healthy adults and for adults with diabetes, and how should they be managed?

Target Fasting Blood Glucose for Adults

For most nonpregnant adults with diabetes on anti-diabetic treatment, target a fasting blood glucose of 80-130 mg/dL (4.4-7.2 mmol/L). 1, 2

Standard Targets for Most Adults

The American Diabetes Association establishes clear glycemic targets that correlate with achieving an A1C <7%: 1

• Fasting/preprandial glucose: 80-130 mg/dL (4.4-7.2 mmol/L) 1, 2
• Peak postprandial glucose (1-2 hours after meals): <180 mg/dL (<10.0 mmol/L) 1, 2
• A1C goal: <7.0% (53 mmol/mol) 1

The 80-130 mg/dL range is based on the ADAG study, which demonstrated that these preprandial targets correlate with optimal A1C achievement while providing a safety margin to prevent hypoglycemia during medication titration. 1, 2 The higher lower limit (80 mg/dL versus the older 70 mg/dL target) specifically reduces overtreatment risk. 2

For Healthy Adults Without Diabetes

Normal fasting glucose is <100 mg/dL (5.6 mmol/L). 3 Values of 100-125 mg/dL define impaired fasting glucose, an intermediate state carrying significant diabetes risk. 3

Algorithm for Individualizing Targets

More stringent targets (closer to 80 mg/dL lower bound or even <7% A1C) are appropriate when: 1, 2

• Newly diagnosed with diabetes 1
• Longer life expectancy (>10-15 years) 1
• No significant cardiovascular disease 1
• No history of severe hypoglycemia 1
• Younger age with few comorbidities 1
• Patient can achieve targets safely without hypoglycemia 1

Less stringent targets (fasting glucose up to 130 mg/dL or higher, A1C up to 8%) are appropriate when: 1, 2

• Limited life expectancy (<10 years) 1
• History of severe hypoglycemia or hypoglycemia unawareness 1
• Advanced microvascular or macrovascular complications 1
• Multiple comorbidities 1
• Advanced age or frailty 1, 4
• Long duration of diabetes with difficult control 1

Continuous Glucose Monitoring Targets

For patients using CGM, parallel targets include: 1, 2

• Time in range (70-180 mg/dL): >70% of readings 1, 2
• Time below range (<70 mg/dL): <4% of readings 1, 2
• Time below 54 mg/dL: <1% of readings 1, 2
• Glycemic variability (coefficient of variation): ≤36% 1, 2

For frail or high-risk patients, acceptable targets are >50% time in range with <1% time below range. 1

Hospitalized Patients

For critically ill and non-critically ill hospitalized adults, target 140-180 mg/dL (7.8-10.0 mmol/L). 1, 2

• Initiate insulin therapy when glucose persistently exceeds 180 mg/dL (checked twice) 1
• More stringent goals of 110-140 mg/dL may be acceptable only for select patients (e.g., post-cardiac surgery) if achievable without significant hypoglycemia 1
• The NICE-SUGAR trial demonstrated that tight control (81-108 mg/dL) in critically ill patients increased mortality compared to moderate targets (140-180 mg/dL), with 10-15 fold higher hypoglycemia rates 1

For non-critically ill hospitalized patients, expert consensus recommends 100-180 mg/dL, though 140-180 mg/dL remains safest for most. 1

Critical Hypoglycemia Thresholds

Understanding hypoglycemia definitions is essential for safe glucose management: 2

• Alert value: <70 mg/dL (3.9 mmol/L) - requires immediate action 2
• Clinically significant: <54 mg/dL (3.0 mmol/L) - associated with neuroglycopenic symptoms 2
• Severe hypoglycemia: altered mental/physical status requiring assistance 2

Common Pitfalls to Avoid

• Never target fasting glucose <80 mg/dL routinely - this increases hypoglycemia risk without additional benefit 2
• Do not pursue aggressive targets in elderly or frail patients - overly tight control (A1C <6.5%) is associated with increased mortality in this population 4
• Avoid focusing solely on fasting glucose - postprandial values contribute significantly to A1C, especially when A1C is closer to 7% 1
• Always deintensify therapy after severe or recurrent hypoglycemia - this is an absolute indication to raise glycemic targets 1
• Do not ignore hypoglycemia unawareness - patients should raise targets for several weeks to partially reverse this dangerous condition 1

When to Deintensify Treatment

Deintensify hypoglycemia-causing medications (insulin, sulfonylureas, meglitinides) when: 1

• Severe or frequent hypoglycemia occurs 1
• Patient has hypoglycemia unawareness 1
• Harms/burdens of treatment exceed benefits 1
• Life expectancy decreases such that benefits of intensive control cannot be realized 1