What is the normal range for Random Blood Sugar (RBS)?

Normal Random Blood Sugar (RBS) Range

A normal random blood sugar (RBS) is generally considered to be less than 140 mg/dL (7.8 mmol/L), though values below 200 mg/dL (11.1 mmol/L) without diabetic symptoms do not confirm diabetes. 1

Diagnostic Thresholds for Random Blood Glucose

For diabetes diagnosis:

• ≥200 mg/dL (11.1 mmol/L) with classic diabetic symptoms (polyuria, polydipsia, weight loss, blurred vision, fatigue) confirms diabetes 1
• Values of 140-180 mg/dL (7.8-10.0 mmol/L) have high specificity (92-98%) for diabetes and warrant definitive testing with fasting glucose or oral glucose tolerance test 1
• Random glucose ≥140 mg/dL (7.8 mmol/L) has 55% sensitivity and 92% specificity for detecting diabetes 1

For normal/non-diabetic range:

• Values <140 mg/dL (7.8 mmol/L) are generally considered within normal limits for random testing 1
• Research suggests that random glucose <100 mg/dL (5.6 mmol/L) is associated with very low diabetes risk 2

Clinical Context and Risk Stratification

The interpretation of RBS values depends heavily on clinical context:

• 100-119 mg/dL (5.6-6.6 mmol/L): Elevated risk zone requiring further evaluation. This range shows 7-fold increased odds of undiagnosed diabetes compared to values <100 mg/dL 2

• 120-139 mg/dL (6.7-7.7 mmol/L): High-risk zone with 30-fold increased odds of undiagnosed diabetes, warranting definitive testing 2

• ≥140 mg/dL (7.8 mmol/L): Very high specificity (92-98%) for diabetes; proceed with confirmatory fasting glucose or HbA1c testing 1

Important Clinical Caveats

Limitations of random blood glucose testing:

• RBS has relatively low sensitivity (39-55%) for detecting diabetes, meaning normal values do not rule out diabetes 1
• Random testing should not be used as the sole diagnostic method; confirmatory testing with fasting glucose (≥126 mg/dL on two occasions) or HbA1c (≥6.5%) is required 1
• Having ≥2 random glucose values ≥115 mg/dL provides 87% sensitivity and 77% specificity for predicting diabetes diagnosis within one year 3

For continuous glucose monitoring (CGM) users:

• Target range is 70-180 mg/dL (3.9-10.0 mmol/L) for type 1 and type 2 diabetes patients 1
• Tighter control targeting 70-140 mg/dL (3.9-7.8 mmol/L) may be appropriate for select patients approaching normal glucose levels 1, 4

Critical hypoglycemia threshold:

• Any value <70 mg/dL (3.9 mmol/L) represents hypoglycemia requiring immediate treatment 5
• Never administer insulin when glucose is <70 mg/dL 5