Understanding "HS Glucose Number"
HS stands for "hora somni" (Latin for "at bedtime"), so your HS glucose number refers to your blood glucose reading taken at bedtime before sleep.
What HS Glucose Means
The term "HS" is standard medical abbreviation used to indicate bedtime glucose measurements. This reading is typically taken:
- Right before going to sleep (not at a fixed clock time like midnight)
- After your evening meal has been digested
- Before taking any bedtime medications or insulin
Clinical Significance of Bedtime Glucose
Your bedtime glucose reading is critically important because it predicts your risk of nocturnal (nighttime) hypoglycemia. 1
Target Bedtime Glucose Ranges
According to current guidelines, the appropriate bedtime glucose target depends on your diabetes management:
- General target for bedtime glucose: <140 mg/dL to guide insulin adjustments 1
- If bedtime glucose is >140 mg/dL: Increase pre-evening meal insulin dose by 10% 1
- If bedtime glucose is <70 mg/dL: Decrease pre-evening meal insulin dose by 10-20% to prevent nocturnal hypoglycemia 1
Predicting Nocturnal Hypoglycemia
Bedtime glucose <7.0 mmol/L (126 mg/dL) is the best predictor of nocturnal hypoglycemia, with 83% accuracy 2. Research shows:
- Bedtime glucose <6.0 mmol/L (108 mg/dL): 71% risk of nocturnal hypoglycemia 3
- Bedtime glucose 7-10 mmol/L (126-180 mg/dL): Any bedtime snack is advised 4
- Bedtime glucose <7 mmol/L (126 mg/dL): Standard or protein snack recommended 4
- Bedtime glucose >10 mmol/L (180 mg/dL): No snack necessary 4
Why Bedtime Glucose Matters More Than You Think
Nocturnal hypoglycemia occurs in 29-37% of insulin-treated patients, and 67% of these episodes are asymptomatic (you won't feel them) 5, 3. This is dangerous because:
- You cannot treat hypoglycemia while asleep and unaware
- Recurrent nocturnal hypoglycemia impairs your ability to recognize future hypoglycemia 6
- It increases risk of severe hypoglycemia requiring assistance
Common Pitfall to Avoid
Do not rely on fasting morning glucose alone to detect nocturnal hypoglycemia. While a fasting glucose <5.5 mmol/L (99 mg/dL) suggests preceding nocturnal hypoglycemia 5, bedtime glucose is the superior predictor for prevention 2.
Practical Monitoring Recommendations
Check your bedtime glucose if you:
- Use insulin (especially basal or prandial insulin) 1
- Are initiating or changing diabetes medications 7
- Have not met treatment goals 7
- Are at risk for hypoglycemia 8
Note: Using clock-based definitions (midnight to 6 AM) may underestimate hypoglycemia while actually asleep, since most people's sleep patterns don't align perfectly with these hours 9.