If you’ve ever checked your glucose with two different meters and gotten totally different numbers — like 75 on one and 115 on the other — you’re not imagining things. You’re also not alone. And if you’ve felt anxious, frustrated, or just plain tired of trying to figure out which number is right, I hear you. Diabetes educators like me have been dealing with this same issue for decades — and trust me, it’s one of our biggest pain points, too.
Let’s break it down, together — honestly, clearly, and with no sugar-coating.
Why Doesn’t the Number Match?
The simple answer is this: glucose meters are old technology. They haven’t changed much since the 1970s. Yes, the 1970s. And the FDA still approves these meters based on a rule that allows a wide range of results to still be considered "acceptable."
That means if your true glucose is 100 (based on a lab test), one FDA-approved meter could read 75 and another could read 115 — 30 points difference! And both would still be considered accurate under FDA standards.
Even worse? The higher your glucose is, the wider that acceptable range gets. For example, if your true glucose is 200 in the lab, and one meter reads 170, while the other reads 230, that 60 point difference is also an FDA approved range.
It’s frustrating. For you. For me. For all of us clinicians.
So which meter should you believe?
The tough truth is that you can’t really rely on any of them to have an EXACT number. But you CAN use that reading and the readings before and after it to get a idea of your trends. And that idea of the trends, along with how you feel, are the best ways to really make sense of the numbers.
- First, believe your body (especially for lows). Check for symptoms. If you are feeling low, then you might truly be. Retest if you can just to verify the reading.
- Second, see if its logical. If you test before and 30-60 minutes after eating a sweet food and it spikes, its likely pretty good. Just watch out for fat and protein, because those will slow down the spike. If you test at the wrong time, you might miss it and think the meter is faulty when its not.
- Third, watch for trends. Don’t look at just one number and freak out. try to see if this is a pattern over time. if you and your clinician can’t make sense of it, then it might really be an error.
Most importantly, NEVER compare one meter to another. The readings will always be off.
So What Matters Most?
The actual number on the meter matters less than:
- The trend (Is it going up or down?)
- The change from before (What happened before vs after you ate? After your walk?)
- How it helps you adjust (Do you need insulin? Water? Food?)
And if you’re working with a health coach, dietitian, or diabetes educator — like us — what we care about most is helping you feel good, stay safe, and live well.
We cover real care. We get paid when you get healthier. Not when you buy more stuff.
So, test as much as you need to feel in control. And if you don’t want to use our meter, that’s okay too. Just don’t go back to a meter that’s failed you before.
Takeaways
You're not alone. This is the nature and limitations of the technology. Continuous glucose monitors (CGMs) are a great option to help you paint a clear picture of the trends, but they are still not for everyone, and also come with their own set of questions.
Until the tech improves, we’ll keep fighting alongside you — and help you make sense of the numbers, one reading at a time.
You’ve got this. We’ve got you.