If your CGM is waking you up at night with alerts, you're not alone. These alarms can be frustrating—but they’re also an important part of keeping you safe while you sleep. Let’s break down why they happen, what they mean, and how you can manage them.
What Are Nighttime CGM Alerts?
Your CGM (Continuous Glucose Monitor) is always working—even while you sleep. If your glucose goes too low or too high during the night, it will alert you. These alarms are designed to:
- Prevent dangerous lows (hypoglycemia) that can happen while you’re unaware
- Warn you of high glucose (hyperglycemia) so you can take action if needed
- Track fast changes in your blood sugar that may need attention
Why Glucose Swings Happen at Night
Here are a few common reasons your CGM may alert you in the middle of the night:
- Too much basal insulin (or long-acting insulin) can lead to lows while you sleep
- Skipped dinner or delayed meals can leave you with less fuel overnight
- Alcohol before bed may drop your glucose several hours later
- Dawn phenomenon causes blood sugar to rise early in the morning (around 3–6 AM)
- Stress, illness, or high-fat meals in the evening can lead to overnight highs
Should I Always Respond to Nighttime Alerts?
If you are not taking any medications that may cause lows, it is more likely to be just an error. In that case, you may want to double check with a glucose fingerstick. However, if you are taking medications that may cause a low glucose, then yes, treat it in the following ways:
- Low alerts (<70 mg/dL): Follow the 15-15 rule—eat 15g of fast-acting carbs and check again in 15 minutes
- High alerts (>180–200 mg/dL): You might need insulin, movement, or hydration (but check with your healthcare team first)
- Rate of change alerts (double arrows): These mean your sugar is changing fast—up or down—and you may need to act sooner
Tips for Sleeping Through the Night Safely
Check out our article discussing CGM accuracy to know what can cause questionable readings.
- Set realistic nighttime alert thresholds—not too sensitive, not too lenient
- Work with your provider to adjust insulin doses if you’re going low often
- Avoid heavy exercise or alcohol close to bedtime
- Use a snack with protein and fat if your glucose tends to drop overnight
- Turn on “Do Not Disturb” but allow critical CGM alerts through
Takeaways: It’s a Balancing Act
Nighttime CGM alerts can feel annoying, but they’re really like a safety net. If they’re happening often, that’s your body telling you something needs adjusting—whether it’s food, meds, or sleep habits.
Talk to your care team if your alarms are going off too frequently. Small changes can help you sleep better and stay in range more often—no late-night wake-up calls needed.