People living with type 1 diabetes (T1D) need to check their blood sugar levels on a regular basis. Without regular checks during both the day and night, blood sugars may get too high (hyperglycemia) or too low (hypoglycemia). While some people opt to monitor their blood sugar (glucose) levels through finger pricks, others choose to use technology like continuous glucose monitors (CGMs).
CGMs are wearable devices that measure glucose levels every one to five minutes and help people with T1D determine if they need to take immediate action to manage their diabetes. CGMs can also help to identify long-term patterns in glucose levels that can be used to adjust diabetes management plans. Through connected apps, CGMs can often generate a full picture of a person’s glucose trends, from current and average levels to increasingly important metrics like time in range. Read on to learn about the power of time in range—what it is, why it matters, and future applications.
What is Time in Range?
Time in Range
Time in range is the percentage of time per day spent within the range of 70 and 180 milligrams of glucose per deciliter of blood (mg/dL).
Time in range is used by people with T1D and their care teams to see how often glucose levels are within the recommended range. Current standards of care recommend that most people with T1D aim for the following targets:
| Glucose levels (mg/dL) | Percent of time per day spent | |
|---|---|---|
| Time Above Range | Greater than 180 | Less than 25% |
| Time in Range | 70-180 | 70% |
| Time Below Range | Less than 70 | 4% or less |
| Less than 54 | 1% or less |
While each person has different glucose targets, most people living with T1D should aim to have their glucose levels in the recommended range, which is considered safe and healthy for most. People with T1D should work closely with their healthcare teams to review CGM data and create personalized high and low alerts, which often change based on time since T1D diagnosis, age, complications, hypoglycemia unawareness, pregnancy, and more.
CGMs also produce 24-hour graphs (as shown in the figure below), which show whether glucose levels are in, above, or below range at different time points throughout the day. Since glucose levels can change day to day, healthcare teams generally review patterns over a 14-day period. Percentage of time spent in, above, or below range coupled with the 24-hour graph are especially helpful in identifying glucose patterns according to time of day.
Time in Range Versus HbA1c
Time in range and 24-hour CGM graphs paint a picture of a person’s glucose patterns throughout the day. People can choose how many days of CGM data they want to review, and reviewing a specific period of time may help individuals better understand how diet, exercise, and illness affect glucose levels. On the other hand, HbA1c is measured through a blood test that reports average blood sugar levels over the previous 2-3 months. Healthcare professionals (HCPs) often use both time in range and HbA1c measurements to get a comprehensive picture of a person’s glucose levels and make the most informed care decisions possible.
Why Time in Range is Important?
The most important feature of time in range (and CGM data) is that it can provide people living with T1D with an extensive overview of how and when their glucose levels change throughout the day. Blood sugars can change based on exercise, meals, stress, hormones, and more—and time in range can help people understand how lifestyle factors come into play for their personal blood sugar management.
“Time in range helps people with T1D better understand glucose patterns that are not captured by HbA1c,” explains Brynn E. Marks, M.D., MSHPEd, Senior Director of Medical Affairs at Breakthrough T1D. “Additionally, CGM can help people to review their glucose patterns in between visits with their diabetes team and allow for more frequent adjustments to their insulin doses. Reviewing and acting on time in range data and glucose patterns identified by CGM can empower people to manage their T1D and to avoid the roller coasters of managing high and low blood glucose that negatively impact quality of life.”
Spending more time in range is becoming increasingly associated with a lower risk of developing complications, although further research is needed to better understand this connection. Time in range is also often used as an outcome measurement in clinical trials to help researchers understand if a new therapy or treatment is improving blood sugar management. So, the benefits of time in range go beyond personal blood sugar trends, and as we continue to improve our understanding of this metric, its applicability in research and beyond will continue to broaden.
What’s Next for Time in Range
Time in Tight Range
Time in tight range, which is also sometimes referred to as time in normal glycemia, is defined as the percentage of time spent with glucose levels between 70 to 140 mg/dL. People without diabetes have a time in tight range of about 96%. As diabetes therapies and technologies continue to advance, we are just beginning to understand the potential clinical benefits of aiming for a narrower glucose range in people with T1D. Researchers suspect that fluctuations outside in time in tight range may be a better predictor of complications risk. Yet, before we integrate time in tight range into clinical decisions, more research is needed to uncover the benefits of this metric and advance therapies and technologies that will allow people to achieve this narrower target without creating additional undo burden.
Automated Insulin Delivery Systems in Clinical Trials
Diabetes technology has advanced tremendously in the past few decades, largely driven by Breakthrough T1D. Right now, we have automated insulin delivery (AID) systems that can automatically increase or decrease insulin delivery based on CGM readings. These AID systems help to improve time in range and time in tight range while decreasing high and low blood sugar levels, but meal announcements are still required. Fully closed loop systems in the pipeline will not require mealtime announcements. This next-generation technology has the potential to help people achieve time in range targets while using less effort to manage T1D. Breakthrough T1D is funding studies to drive innovation in fully closed-loop systems and bring newer generations to the T1D community quickly and safely.
Non-Insulin Therapies
Therapies used alongside insulin and AID systems have the potential to improve both blood sugar levels and metabolic health. Breakthrough T1D is funding studies investigating treatments that can address insulin resistance, weight management, hypoglycemia, and long-term complications. The goal is to customize treatment approaches and ensure that the T1D community can choose from multiple drugs that may best manage blood sugars and overall health.
GLP-1 in Clinical Trials
The Breakthrough T1D-funded ADJUST-T1D clinical trial showed that the GLP-1 receptor agonist semaglutide (Ozempic) can improve blood sugar and weight outcomes in adults living with T1D and overweight or obesity. After 26 weeks, people treated with semaglutide showed greater improvements in both time in range and time in tight range compared to those who received the placebo. This study has provided evidence for the potential of this class of drugs to benefit the T1D community, and Breakthrough T1D is continuing to drive research into this area.
While exciting advancements in treatments and devices are coming down the pike, many people living with T1D are still unable to reach time in range goals with the tools currently available. Access to improved technologies and non-insulin therapies that can help people with T1D achieve optimal glucose targets will make it possible to use time in tight range goals as the standard of care. Because glucose targets are personalized, time in tight range may not be the right metric for everyone, and more research is needed to see which populations may benefit the most. In the meantime, Breakthrough T1D is working tirelessly to improve the lives of the T1D community, help people achieve the best blood sugar management possible with the options available now, and accelerate the next breakthroughs through the pipeline.
“In the future, I think we will see greater use of time in range in T1D management by people with T1D and care providers as adoption of CGM continues to increase. A growing body of evidence suggests that greater time in range, like low HbA1c, is associated with a lower risk of developing long-term complications. These data might not only support CGM use and attention to time in range in clinical decision-making, but may also impact the way new therapies are evaluated. Today, time in range is widely accepted as a means to evaluate AID systems, but we are not there yet when it comes to evaluating new drugs. Finally, there is a lot of ongoing research to understand time in tight range and how this will help us with clinical guidance and therapy development in the future.”
-Jonathan Rosen, Ph.D., Director of Research at Breakthrough T1D
Improving the Lives of the T1D Community
The goal of Breakthrough T1D’s Improving Lives Program is to ensure that people with T1D have the highest quality of life possible while cures are on the way. We are actively supporting research to drive innovation in technology and devices and understand how new and repurposed medications can improve blood sugar levels, reduce the risk of long-term complications, and benefit overall health. We are clearing approval and coverage pathways for these advancements through our advocacy work and enhancing clinical adoption of devices to improve blood sugar management in more people than ever. Until cures are widely available, Breakthrough T1D will continue to improve the lives of those living with T1D now.
