Managing blood glucose levels is a crucial part of living with type 2 diabetes. Time in range (TIR) is a part of continuous glucose monitoring (CGM) that can help inform long-term treatment and support comprehensive glucose regulation.

Diabetes is a chronic health condition that develops when the body cannot effectively use or produce insulin, a hormone that regulates levels of glucose, or sugar, in the bloodstream.

According to the Centers for Disease Control and Prevention (CDC), type 2 diabetes is the most common type of diabetes, and 90–95% of people with diabetes have this type. It develops when the body does not properly use insulin, causing glucose levels in the bloodstream to become too high.

Monitoring glycemia, or glucose levels, is an important part of managing diabetes and preventing complications. This article looks at the role of time in range (TIR) for type 2 diabetes, how it compares to other metrics, and who may be a candidate to use it.

TIR is a measurement of how long someone spends within their optimal blood glucose range over the course of a day. It is a percentage based on data a person collects through continuous glucose monitoring (CGM).

CGM involves taking regular blood sugar readings throughout the day. A person uses an external monitoring device attached to a sensor under the skin that takes readings at set intervals.

A person can use a specialized reader or smartphone to track the results and calculate them over time into TIR.

Glycemia goals can vary from person to person, but the standard range is 70–180 milligrams of glucose per deciliter of blood (mg/dL).

According to the American Diabetes Association (ADA), most people living with type 2 diabetes should stay within that range at least 70% of the time, or 17 hours of a 24-hour day.

Additionally, general guidelines for any time not within optimal range include:

  • less than 4% of time below 70 mg/dL
  • less than 1% of time below 54 mg/dL
  • less than 25% of time above 180 mg/dL
  • less than 5% of time above 250 mg/dL

Glucose targets for people living with type 2 diabetes can vary based on age, risk factors, and health status.

The 2019 ADA TIR guidelines define these variations for type 2 diabetes as follows:

Category of type 2 diabetesTarget glucose rangeRecommended TIR
typical (in people ages 25 years and older)70–180 mg/dLgreater than 70%
typical (in people under 25 years of age)70–180 mg/dLgreater than 60%
type 2 diabetes in people who are older or high risk70–180 mg/dL greater than 50%
gestational type 2 diabetes in pregnancy63–140 mg/dL greater than 90%

Research from 2022 includes an additional variation for diabetes with frailty, a unique presentation of diabetes co-occurring with age-associated frailty syndrome:

Category of type 2 diabetesTarget glucose rangeRecommended TIR
diabetes with frailty70–180 mg/dL greater than 50%

A1C testing, also known as hemoglobin A1C or HbA1c testing, has been a staple in glycemic monitoring since the 1960s.

It measures the amount of red blood cells, or hemoglobin, in the blood that have attached glucose. Because red blood cells have a life span of about 4 months, the A1C reflects a person’s average blood glucose levels over several months.

Like TIR, A1C is a percentage. Optimal levels are considered to be under 5.7%.

In recent years, there has been a strong push to use TIR over A1C as a way of providing deeper insight into real-time blood sugar regulation. Rather than using one number as representative of 4 months, the TIR is a daily diary of patterns in someone’s blood sugar management.

According to a 2020 review, the main limitation of the A1C is that it provides only a summary of glucose levels without details that might be important, such as spikes or drops in blood sugar throughout the day.

The following factors can also affect the accuracy of A1C measurements:

  • anemia
  • pregnancy
  • certain hemoglobin disorders
  • liver disease
  • race and ethnicity

This does not mean the A1C is outdated or lacks value. Healthcare professionals still consider it a valuable tool for assessing overall blood sugar regulation and screening for diabetes and related complications.

The ADA notes that TIR can be the most beneficial for people with type 2 diabetes who use insulin and have a narrow range of optimal blood sugar compared to the standard.

This is because the tighter someone’s target blood sugar range is, the more likely they are to find themselves outside that range.

Even when someone’s blood sugar range is typical, doctors may recommend CGM and TIR. The more frequently a person does CGM throughout the day, the more precisely they can monitor their blood sugar levels.

Ultimately, anyone who is interested in improving the accuracy of their blood sugar tracking can use TIR.

CGM is not yet a popular strategy, despite its noted benefits. The ADA indicates that this may be due to costs and a lack of insurance coverage for diabetes supplies, though policies are improving.

Anyone who is interested in learning more about CGM and TIR should speak with a doctor familiar with this type of glycemic management. A working relationship with a doctor is necessary to properly interpret the results of CGM and TIR and determine individual glucose targets.

The Endocrine Society recommends that a person ask the following questions during an initial consultation when considering CGM and TIR:

  • Does CGM fit into my current diabetes management plan?
  • Can you help me learn more about my personal TIR targets?
  • Can my diabetes medications cause hypoglycemia (low blood sugar)?
  • What changes would I need to make to start using CGM?
  • Should I consult a diabetes educator or specialist?
  • Should I consult an endocrinologist?
  • If I develop hypoglycemia, what should I do?
  • Can I get an emergency glucagon kit?
  • What important information should my loved ones know about CGM and hypoglycemia?

Time in range (TIR) is a measurement of how long someone’s blood glucose is within their target range over the course of a day. It is a way for people with diabetes to track glucose levels in real time and improve their diabetes management strategies.

The following websites offer more information on TIR and CGM:

Most people living with type 2 diabetes could gain insights from CGM and TIR, though these measurements may be most beneficial for people with tighter target blood sugar ranges.