The New Report Cards: Your Patient's CGM Data

This transcript has been edited for clarity. 

Matthew F. Watto, MD: Welcome to The Curbsiders. I'm Dr Matthew Frank Watto, here with my great friend and America's primary care physician, Dr Paul Nelson Williams. Paul, we're going to be talking about continuous glucose monitors (CGMs). Have you ever heard of those before? 

Paul N. Williams, MD: Yeah, once or twice. Patients might ask about them, so this might come up in your practice. 

Watto: Yes, I was super-excited about this podcast. Our great friend, Dr Jeff Colburn, walked us through this. He approached us to do this episode because in April 2023, the Centers for Medicare & Medicaid Services made this ruling that anybody with diabetes who is on a single dose of insulin per day, or who's having recurrent severe hypoglycemia, should qualify for a CGM. It has really unlocked this for a lot of people, because prior to that time, people had to be on a basal bolus, three or four times a day dosing of insulin, to qualify. But now CGMs are available to a lot more patients. 

Williams: It's such a gift because it took an act of Congress to get one of these things for someone when they first came out. Now it's becoming almost a standard of care for anyone who's on injectable medication. It has really opened things up in terms of how we're able to take care of patients and give them a little more tailored guidance that is more objective. 

Watto: So, Paul, what kind of information are patients going to be getting from the CGM, or what is the clinician receiving in the office when patients bring in their CGMs — their cell phone apps that have this data? What sort of metrics are we going to be tracking? 

Willilams: The overall approach or the thing that you're looking at — and it's neat because patients love report cards — will tell you specifically the time in the desired glucose range. 

The goal is for the patient's blood glucose to be between 70 mg/dL and 180 mg/dL over 70% of the time, which makes good sense. The thing we want to avoid the most is hypoglycemia, which you really want to be less than 5% of the time. That's defined by most of these devices as a blood glucose of less than 70 mg/dL. And then there's a time above range, which is when the patient is hyperglycemic, or greater than 80 mg/dL. They should be there less than 30% of the time. That time in range, at least in my experience, is the metric that the patients really fixate on, and they feel like they can celebrate when that number is in the green zone (higher than 70%).

Watto: That's right. Because it's color-coded. The app is like a stoplight: red for lows, green for in-range, and yellow for the high levels. Patients can follow that. 

Williams: The neat thing is the variances which can then help tailor your management. If someone is having hypoglycemia more often, you can actually match the patterns to the kind of insulin you're giving them. 

Watto: They have a sort of graphic overlay, which is essentially the time and the glucose level throughout the day. You can see a thin line that shows their average glucose level throughout the day at certain times of day. But then it also shows you the swings. You may see a big hump after a certain meal when their blood glucose goes very high, or a certain time of day when they tend to go low. And you can use that to match their pattern to the treatment. So, let's talk about some of the common patterns that we see. 

The first thing you want to do when you're looking for patterns is to look for hypoglycemia, because that's what can kill the patient. Even if you're seeing highs and lows, you have to address the hypoglycemia first. Once you've targeted the hypoglycemia, you go after the hypoglycemia. 

Try to fix the fasting blood sugars first. Those are generally easiest to fix. A lot of us in primary care are used to using either metformin or basal insulin, which are good for targeting the fasting glucose. And then the final thing you would target is the postprandial glucose. What is the glucose doing after meals? It sounds simple, but I don't know that anyone has ever told me clearly how we should be approaching this. 

Williams: It feels like it should be intuitive. I knew the general principles, but actually hearing Jeff explain these things, it really brought remarkable clarity to it. 

Watto: Remember when Dr Colburn was talking about the hypoglycemia and one of his patients said, "Can I just let my body fix the hypoglycemia?" He told him no, that's bad, because the counterregulatory hormones are very bad for you — epinephrine, norepinephrine, cortisol — they all stress the heart. You don't want to be putting your body through that all the time. 

You made the point about the type of foods patients tend to keep around when they have hypoglycemia. What are they eating? Generally not the best things? 

Williams: It's almost invariably the worst garbage in the world. I think I've had patients with drawers full of cookies. I'm not knocking these patients because hypoglycemia is awful and you feel terrible, and it's dangerous. So I don't begrudge them that. But a better way is something like a banana with peanut butter so they get some protein and also some carbohydrates to kind of gently control things, as opposed to just blasting themselves with Jolly Ranchers. 

Watto: Banana and peanut butter is a great snack before they exercise too because it has some carbs, some fats, and some protein. It's not going to just spike their blood sugar super-high. 

Dr Colburn also told us that if the patient is having nocturnal hypoglycemia and you reduce their basal insulin dose and omit the evening sulfonylurea dose (if taken twice daily) and reduce or stop long-acting sulfonylurea agents, their A1c may actually improve, even though you are reducing their medications. When you have hypoglycemia, the body's counterregulatory hormones are spiked up for the next 24 hours and insulin sensitivity declines, which makes sense; you don't want the body to be super-responsive to insulin. That's why preventing hypoglycemia can actually improve the A1c without adding medication. 

We go into a ton of this with Dr Colburn — a lot of nitty-gritty details that are super-useful in your practice. So please check out the complete podcast at CGMs, Insulin, and How to Adjust Diabetes Meds to Glucose Patterns.