Getting your first Continuous Glucose Monitor (CGM) is a big step! CGMs like the Dexcom and Freestyle Libre are powerful tools that give you real-time feedback about your blood sugar. They can help you spot patterns, avoid dangerous highs or lows, and feel more in control of your health.
But for many people, the first few days can also feel overwhelming. It’s normal to feel anxious when you’re suddenly getting alerts at night or seeing numbers that don’t quite match your fingerstick meter. The key is knowing what’s normal, what’s a glitch, and what’s worth double-checking.
Here’s what every new CGM user should know.
Why Readings May Seem “Off” in the First 24–48 Hours
When you first insert a sensor, it takes some time for it to settle into the interstitial fluid (the fluid under your skin where the CGM measures sugar). During the first day or two:
- Readings may run a little higher or lower than your fingerstick.
- You may see false alarms for lows or highs.
- This is temporary—accuracy usually improves after 24–48 hours.
👉 Tip: If you’re starting a new sensor, give yourself grace. Don’t panic if your numbers look unusual the first day.
What Are “Pressure Lows”?
One of the most common false alarms happens when you’re sleeping. If you lie on the arm or stomach where your CGM is placed, the pressure can slow blood flow around the sensor. The sensor then “thinks” your blood sugar is dropping quickly—even if it’s not. You may wake up to a low alarm, only to check your meter and find that you’re perfectly fine.
👉 Tip: If you get frequent nighttime alarms that don’t match your symptoms, check your sleeping position. Try switching the sensor to a spot where you don’t put as much pressure while resting.
When to Double-Check With a Fingerstick
CGMs are excellent tools, but they aren’t perfect. Always use a fingerstick reading when:
- Your CGM says you’re low, but you don’t feel symptoms (shakiness, sweating, confusion, fast heartbeat).
- Your CGM says you’re high, but it doesn’t match how you feel.
- The reading seems to change very quickly and feels “off.”
A true low blood sugar is confirmed by:
- A fingerstick reading showing low glucose (usually <70 mg/dL).
- Symptoms of low blood sugar, like dizziness, sweating, hunger, or shakiness.
A false low is when:
- The CGM shows a low number, but your fingerstick is in range.
- You feel fine and have no symptoms.
👉 Rule of thumb: Trust your symptoms + fingerstick before taking action.
Tips to Reduce False Alarms
- Pick the right site. The primary application site is the back of the upper arm. Choose an area with some fat, avoid scar tissue, and rotate sites to keep accuracy.
- Check alarm settings. Set your low alarm at a level that feels safe but not too sensitive (e.g., 70 mg/dL instead of 80 mg/dL if you’re waking up too often at night). Set a “snooze” time so the alarm doesn’t keep repeating for the same reading.
- Be mindful of compression. Try not to sleep directly on the sensor. If you get frequent pressure lows, experiment with different placement sites.
- Stay calm with alerts. Remember: an alarm is just a heads-up, not an emergency in itself. Always double-check before correcting.
How to Manage or Silence Alarms
Dexcom G6/G7:
- Open the Dexcom app on your phone.
- Tap Settings → Alerts.
- From here, you can adjust high/low thresholds, change sound/vibration, or temporarily silence alerts.
- “Snooze” lets you choose how often the alarm repeats.
Freestyle Libre 2/3:
- Open the LibreLink app (or check your reader device).
- Go to Alarms Settings.
- You can turn individual alarms (low, high, signal loss) on or off.
- You can also adjust sound, vibration, or snooze times.
👉 Important note: Turning off alarms may reduce anxiety but can also mean missing a true low. If you silence alarms, consider lowering the volume during the night instead of turning them off completely.
Quick Troubleshooting Checklist
- Alarm but no symptoms? → Fingerstick before acting.
- Numbers bouncing a lot on the first day? → Likely sensor warm-up. Give it 24–48 hours.
- Low alarm while sleeping on it? → Try moving to a new site next time.
- Alarms waking you up often? → Adjust thresholds or snooze settings.
The Takeaway
Your CGM is a powerful tool—but like any tool, it takes practice to use it well. Remember:
- The first 24–48 hours may not be perfectly accurate.
- Pressure lows (especially at night) are common and usually false.
- Fingerstick + symptoms are the best way to confirm what’s really happening.
- Alarms can be customized so you feel supported, not stressed.
Once you get used to your CGM, you’ll learn to trust it for the patterns and trends that matter most. With time, the alarms will feel less scary and more like a gentle safety net.
👉 Bottom line: Don’t let the beeps and numbers scare you off. Your CGM is here to help you live with more confidence, not more stress.