Time in Range: How CGM Metrics Help You Manage Diabetes Daily

Most people with diabetes know their HbA1c number. It’s the lab test that tells you your average blood sugar over the last three months. But here’s the problem: two people can have the same HbA1c - say, 7% - and one could be spending most of their day with dangerous highs and lows, while the other stays steady. That’s where time in range changes everything.

What Time in Range Really Means

Time in range (TIR) isn’t a fancy term - it’s simple. It’s the percentage of time your blood glucose stays between 70 and 180 mg/dL (3.9 to 10.0 mmol/L). That’s the sweet spot. Not too high, not too low. Most experts agree you should aim for at least 70% of your day - about 17 hours - in that range. For someone using a continuous glucose monitor (CGM), that’s not a guess. It’s a fact. CGMs check your glucose every 5 minutes, giving you over 1,300 data points in just two weeks. That’s more than a thousand snapshots of your body’s response to food, sleep, stress, and movement.

Before CGMs, we only had HbA1c. Think of HbA1c like reading the summary of a book. You know the ending, but you miss all the drama in between. TIR is reading the whole book. You see when your sugar spikes after lunch. You notice the dip after evening walks. You catch the 3 a.m. crash you never knew about.

Why TIR Beats HbA1c for Daily Life

HbA1c doesn’t tell you if you’re having five hypoglycemic episodes a week. It doesn’t show you that your blood sugar rockets to 220 mg/dL every time you eat oatmeal. It hides the peaks and valleys. That’s dangerous. Hypoglycemia can lead to falls, confusion, even seizures. Chronic hyperglycemia increases your risk of nerve damage, kidney disease, and vision problems.

Studies show that for every 10% increase in time in range, your risk of complications drops significantly. A 2025 study in the Journal of Clinical Endocrinology & Metabolism found that people who spent more than 70% of their day in range had 40% fewer hospital visits for glucose-related emergencies than those who didn’t - even when their HbA1c was the same.

And here’s the kicker: you can improve your TIR without changing your HbA1c target. You don’t need to chase a 6% A1c. You just need to smooth out the ride. That’s why the American Diabetes Association’s 2025 Standards of Care now say CGM and TIR should be considered for everyone with type 2 diabetes on glucose-lowering meds - not just insulin users.

The Other Numbers That Matter

TIR isn’t the only metric. It’s part of a bigger picture. Your CGM also tracks:

• Time Below Range (TBR): Time spent under 70 mg/dL. Aim for less than 4% of the day. Less than 1% should be under 54 mg/dL - that’s severe hypoglycemia.
• Time Above Range (TAR): Time over 180 mg/dL. You want this under 25%. The lower, the better.
• Glucose Variability: How much your numbers swing. High variability means more stress on your body, even if your average looks fine.

One patient I worked with in Sydney had an HbA1c of 6.9% - great, right? But his TIR was only 52%. He was spending nearly 8 hours a day above 180 and over 2 hours below 70. He thought he was doing well. His CGM showed he was playing Russian roulette with his health. After adjusting his evening snack and timing his metformin, his TIR jumped to 74% in six weeks. His HbA1c didn’t change much - but his life did.

How to Use TIR Data in Real Life

Having the data is useless if you don’t act on it. Here’s how to turn numbers into action:

1. Look for patterns. Are your numbers high every Monday morning? Maybe you’re eating more carbs over the weekend. Are you crashing after 3 p.m.? Maybe your lunch is too heavy on refined carbs.
2. Test one thing at a time. Don’t change your diet, exercise, and meds all at once. Try swapping white rice for quinoa for three days. See what happens.
3. Use your CGM’s alerts. Set low and high alerts. You’ll catch trends before they become crises.
4. Share your reports. Don’t just show your doctor your HbA1c. Bring your 14-day CGM report. Highlight the spikes, the dips, the good days. Ask: “What’s causing this?”

One woman in Melbourne discovered her “healthy” granola bar spiked her glucose to 210 mg/dL. She’d been eating it for years thinking it was good for her. With TIR, she found a better option - and saved herself from years of hidden damage.

Getting Started with CGM

If you’re not using a CGM yet, here’s what you need to know:

• Wear time matters. You need at least 70% of your CGM sensor active to get reliable TIR data. That means 10+ days out of a 14-day wear period.
• It’s not just for insulin users. The 2025 ADA guidelines now support CGM for anyone with type 2 diabetes on metformin, SGLT2 inhibitors, GLP-1s, or other glucose-lowering drugs.
• Insurance coverage is improving. In the U.S., Medicare now covers CGM for type 2 patients meeting certain criteria. In Australia, private insurers are starting to follow suit. Check with your provider.
• Don’t skip education. Your diabetes educator can help you interpret the graphs. Don’t try to decode the spikes alone.

CGM devices from Dexcom, Abbott, and Medtronic are more accurate and affordable than ever. The market grew from $4.8 billion in 2022 to an estimated $18.6 billion by 2030 - not because of hype, but because people are seeing results.

What’s Next for Time in Range?

Researchers are now looking at “time in tight range” - staying between 70 and 140 mg/dL. That’s the range most people without diabetes stay in. It’s harder to achieve, but early data suggests it may lower long-term risks even more.

Artificial intelligence is starting to predict your glucose spikes before they happen. One system in development can tell you, “Your sugar will rise in 45 minutes if you eat that pasta. Try adding vinegar to your meal.” That’s not sci-fi - it’s coming fast.

The goal isn’t perfection. It’s progress. You don’t need to be in range 100% of the time. You just need to be in range more than you’re out. Every extra hour you spend in range is an hour your body isn’t under stress.

Final Thought: Your Body Tells You Everything

For decades, diabetes care was based on averages. We measured once a quarter. We made decisions in the dark. Now, we have real-time feedback. Your body is talking. CGM and TIR are the tools that let you listen.

You don’t need to be perfect. You just need to be aware. And with TIR, you’re no longer guessing what’s happening between your doctor visits. You’re in control - one glucose reading at a time.