Time in Range: How CGM Metrics Can Transform Diabetes Management

For people living with diabetes, managing blood sugar isn’t just about hitting a single number once every three months. It’s about staying steady-day after day, meal after meal, hour after hour. That’s where time in range comes in. Unlike HbA1c, which gives you a three-month average, time in range (TIR) shows you exactly how much of your day your glucose levels are staying safely between 70 and 180 mg/dL. And for the first time, this metric isn’t just for people on insulin. The 2025 American Diabetes Association (ADA) Standards of Care now recommend continuous glucose monitoring (CGM) for nearly all adults with type 2 diabetes who are taking glucose-lowering medications. This isn’t a minor update. It’s a shift in how we think about control.

What Exactly Is Time in Range?

Time in range isn’t a guess. It’s a precise number calculated from thousands of glucose readings taken every 5 minutes by a CGM device. If your sensor records your blood sugar between 70 and 180 mg/dL for 17 out of 24 hours, your TIR is 70%. That’s the target most clinicians recommend for adults with type 1 or type 2 diabetes. The goal? Spend at least 70% of your day in that sweet spot.

But TIR doesn’t just tell you if you’re in range. It shows you when you’re out of it. Time Below Range (TBR) flags low glucose events-those scary drops under 70 mg/dL. Time Above Range (TAR) catches the spikes after meals or during stress. Together, these numbers paint a full picture. Two people could have the same HbA1c of 7.0%, but one might be spending 80% of their day in range with only 1% below, while the other swings wildly between highs and lows, hitting 50% in range and 10% below. Their HbA1c looks the same. Their risk? Not even close.

Why TIR Beats HbA1c Alone

HbA1c is like reading the summary of a book. You know the ending, but you miss all the twists. TIR is reading the whole story. You see the late-night lows, the post-lunch spikes, the sugar crash after a walk. These patterns matter because they’re linked to real outcomes: hypoglycemia can lead to falls or car accidents. Chronic highs increase your risk of nerve damage, kidney disease, and vision loss.

Research shows that every 10% increase in TIR is linked to a 15-20% reduction in the risk of diabetic retinopathy progression. That’s not theoretical. It’s from large studies tracking people over years. And here’s the kicker: you don’t need perfect numbers to see results. Moving from 50% to 60% TIR-just 2.5 extra hours a day-can reduce hypoglycemia episodes by nearly half. That’s life-changing for someone who’s terrified of lows.

And unlike HbA1c, which only updates every few months, TIR gives feedback in real time. You can see how that extra slice of pizza affected your numbers by 10 p.m. You can adjust your evening insulin dose before bed, not after the damage is done.

How CGM Makes TIR Possible

CGM devices-like Dexcom G7, Abbott FreeStyle Libre, or Medtronic Guardian-are small sensors worn on the arm or belly. They measure glucose in the fluid under your skin, sending updates to your phone or watch every 5 minutes. Over 14 days, that’s over 4,000 data points. That’s not just data. It’s a map of your body’s response to food, sleep, stress, and activity.

These devices don’t need fingerstick calibration anymore. Most are factory-calibrated and last up to 14 days. You don’t have to prick your finger unless you’re feeling symptoms and the reading doesn’t match how you feel. The data syncs automatically. Apps show you trends, not just numbers. You can see if your glucose rises every time you eat rice, or drops after evening walks. That’s personal insight you can’t get from a lab test.

Who Should Be Using TIR?

For years, CGM was mostly for people on insulin. Now, the ADA says: if you’re taking metformin, GLP-1 agonists, SGLT2 inhibitors, or even sulfonylureas, you should consider CGM. Why? Because even non-insulin users get dangerous highs and lows. A 2023 study found that 38% of adults with type 2 diabetes on oral meds had at least one hypoglycemic episode in a month-many didn’t even know it.

Older adults, people with kidney disease, or those with a history of severe lows benefit the most. TIR helps prevent dangerous drops that could lead to hospitalization. Even people with prediabetes or gestational diabetes are starting to use CGM to understand how their body responds to food before full-blown diabetes develops.

And it’s not just for adults. Teens with type 1 diabetes using CGM report feeling more in control, less anxious, and more confident at school and sports. Parents report fewer nighttime checks because the alarm tells them when glucose is dropping.

Getting Started with TIR

Here’s how to begin:

1. Ask your doctor about CGM eligibility. With the 2025 ADA guidelines, coverage is expanding. Medicare now covers CGM for type 2 diabetes patients on multiple daily injections or insulin pumps.
2. Choose a device. Dexcom and Libre are the most common. Libre doesn’t require a transmitter and reads with a phone scan-easier for some. Dexcom gives real-time alerts.
3. Wear it for at least 14 days. Don’t skip days. You need 70% active wear time for the data to be reliable.
4. Review your report with your diabetes educator. Look for patterns: Are you high after breakfast? Low after gym? That’s where you make changes.
5. Adjust one thing at a time. Maybe it’s eating protein before carbs, or moving your evening walk to after dinner. Small tweaks add up.

Most people need 1-2 visits to learn how to read their reports. Don’t try to fix everything at once. Focus on reducing Time Below Range first. Safety comes before perfection.

Real-Life Impact: Stories from the Field

One man in Birmingham, 62, with type 2 diabetes, was told his HbA1c was 7.2%-"good enough." But his CGM showed he was in range only 45% of the time. He was dropping below 60 mg/dL three times a week, often at night. He didn’t feel symptoms. He thought he was fine. After adjusting his bedtime snack and shifting his metformin dose, his TIR jumped to 75% in 6 weeks. His lows disappeared. He stopped waking up exhausted.

A woman in her 40s noticed her glucose spiked after eating "healthy" oatmeal. Her CGM showed a 220 mg/dL peak. She switched to steel-cut oats with chia seeds and protein. Her post-meal spikes vanished. She didn’t change her calories. She changed her timing and combo. That’s the power of TIR.

Challenges and What to Watch For

CGM isn’t perfect. Sensors can fall off. You might get false alarms. Some people feel overwhelmed by the data. That’s normal. Start simple. Focus on just TIR and TBR for the first month. Don’t obsess over every spike.

Cost is still a barrier. In the UK, NHS access is limited. Private CGM can cost £50-£100 per sensor. But prices are dropping. Abbott’s Libre Sense glucose biosensor is now available over-the-counter in some pharmacies. Insurance coverage is improving-especially since the 2025 ADA guidelines.

And while TIR is powerful, it’s not a replacement for HbA1c. Use both. TIR shows you daily control. HbA1c confirms long-term trends. Together, they’re the best team you’ve got.

The Future of TIR

Next up? "Time in tight range"-keeping glucose between 70 and 140 mg/dL. That’s the range most people without diabetes stay in. Early studies suggest it may further reduce complications. AI tools are being built to predict spikes before they happen, suggesting insulin doses or meal swaps automatically.

By 2030, the global CGM market is expected to hit $18.6 billion. That means more innovation, lower prices, and better access. What’s clear: TIR is no longer a luxury. It’s becoming the new standard of care.

If you’re managing diabetes, your goal shouldn’t be just a "good" HbA1c. It should be spending most of your day feeling stable, confident, and free from the fear of highs and lows. That’s what time in range gives you. Not a number. A life.