So, you’ve been prescribed a fancy continuous glucose monitor (CGM) – wonderful! This little technical wonder is a convenient way to monitor your blood sugar continuously using a small sensor. It helps you understand how your day-to-day activities – like physical activity, sleep, and meal patterns –impact your blood sugar readings.

But the question remains: To stick or not to stick?

The short answer? Yes. Using a fingerstick with a standard blood glucose meter (BGM) is still helpful. The good news is you may not need to poke your finger as often. Let’s review some important times when fingersticks can save the day!

Two Times When You Really Need the Glucometer

1. When Your new CGM Patch is Warming Up

All CGMs have a "warm-up" period after you put a new patch on. This allows the sensor time to settle in the tissue, begin detecting glucose levels, and display readings. In general, warm-up times vary from 30 minutes to 2 hours based on the model:

• Dexcom G7: ~30 minutes
• Dexcom G6 & Medtronic Guardian: ~2 hours
• FreeStyle Libre 2 & 3: ~1 hour

But what if you just ate, are about to eat, or suspect a low? Enter your reliable backup: the blood glucose meter (BGM)! During warm-up, a fingerstick is the only way to get a reading. While you can plan your sensor changes, life is unpredictable, and sometimes a fingerstick is just faster and easier.

2. When You Run Out of Supplies

Sometimes CGM sensors fall off, malfunction, or you simply run out due to cost or availability. No worries – your trusty glucose meter is a reliable backup. Keeping your meter nearby ensures you're never without a way to check your blood sugar.

Checking for Accuracy

Use your old fashioned glucometer whenever you're suspicious of your CGM readings. Here are key times to double-check:

• After inserting a new CGM sensor – readings may be less accurate during the first 30 minutes to 2 hours.
• During rapid blood sugar changes – after high-carb meals, exercise, or alcohol use.
• When symptoms don’t match your CGM – if you feel high or low, play it safe and confirm with a fingerstick.
• During illness or stress – these can cause unpredictable fluctuations.
• Toward the end of your CGM’s lifespan – accuracy may decrease as the sensor nears its expiration.

Remember: Why Your Fingerstick Leads and Your CGM Follows

When it comes to fingersticks, it’s important to remember that BGMs and CGMs sample glucose from different sources:

• BGM (fingerstick) uses capillary blood, which reflects real-time glucose levels.
• CGMs measure interstitial fluid, which lags 5–15 minutes behind during rapid changes.

Think of it like a train:

• 🚂 The blood glucose meter is the engine. The engine leads, showing where the train is right now – just like a BGM gives an instant snapshot.
• 🚃 The Continuous Glucose Monitor is the Caboose. The caboose follows – a few minutes behind – like CGMs, which lag slightly due to how interstitial fluid reflects glucose.

That’s why it’s helpful to keep your BGM on standby – especially during times when your blood sugar may be changing quickly. Now, let’s keep this train rolling and get to the takeaways.

The Takeaways

• You still need a fingerstick meter – even with a CGM, it's a necessary tool.
• Use it during warm-up periods, rapid changes, symptoms mismatch, illness, or sensor expiration.
• BGMs give immediate readings, while CGMs offer trends, but with a slight delay.
• Always have a BGM ready, especially when traveling, sick, or troubleshooting your CGM.
• For additional information, check out these great articles over why your CGM may not match your fingerstick and getting to know your CGM numbers.