How to Calculate + Use Time-in-Range with a BGM
TIR has been mainly discussed when using a CGM, but knowing your TIR is important for every person with diabetes. Since many people with type 2 diabetes use a blood glucose monitor (BGM) to measure their blood glucose levels, they should know how to calculate their TIR.
TIR is what percentage of the day your blood glucose levels are within your target range. The standard target range for an adult with any type of diabetes is approximately 3.885 to 9.99 mmol/l70 to 180 mg/dL for 70% of the day. Your age and other factors help determine ideal targets for you!
However, target ranges should be unique for each person and decided with your healthcare provider. Once you’ve established personal target range goals, your TIR results can help you and your healthcare team determine if your current diabetes regimen is working for you, or if adjustments are needed.
Using TIR to reach A1c goals
You can estimate what your next A1c result is based on how often you are within your target range.
For example, if you are within your target range about 70% of the day, meaning your blood sugars are either lower or higher than your target the other 30%, you can predict an A1c of around 7%. (You’ll learn how to calculate TIR in a moment!)
(You can also look at your average blood sugar level and translate it into an A1c result.)
Although A1c has been the gold standard for assessing the effectiveness of diabetes treatments, TIR may be more helpful. Most A1c tests are done every three months, leaving a large gap of time before making any necessary medication or lifestyle adjustments.
Since A1c is a measurement of average glucose levels over a three month period, it may also not show how often a person is experiencing severe lows or highs fluctuations in blood glucose levels.
If a doctor only looked at a patient’s A1c, they may not know, for example, that you’re frequently dropping below 2.775 mmol/l50 mg/dL every night or rising above 16.65 mmol/l300 mg/dL. Without those details, they can’t make thoughtful adjustments to your insulin and medication dosages or offer helpful diabetes education.
TIR can also be more helpful in clearly showing how your body is responding to new medications or lifestyle changes.
Calculating TIR with a BGM
TIR is not just for CGM users. If you use a blood glucose monitor to measure your blood glucose levels, you can manually calculate your TIR. Here are the steps for calculating your TIR with BGM measurements.
- Check your blood glucose levels as often as you can over a 14-day span. You can check 2 hours after a meal, fasting, bedtime, etc. Aim for at least 6 to 8 checks per day.
- You count the number of readings (from the entire 14-day span) that were within your target range and divide it by the total number of blood glucose readings. Standard target ranges are usually between 70 mg/dL and 180 mg/dL, but you should discuss if this range is right for you with your doctor.
(# of readings within target range ÷ total # of readings) × 100 = %TIR
Here’s an example:
You checked your blood glucose levels 100 times these past two weeks. Of those 100 readings, 50 were within the 70 to 180 mg/dL range. You’ll take that 50 and divide it by 100, to get 0.50. Next, you’ll multiply that by 100 to get your time in range, which would be 50%.
(50 ÷ 100) × 100 = 50% TIR
This means that your blood glucose levels are within your target range 50% of the time.
What should my TIR goal be?
Calculating your TIR is the first step. The next step is to understand your TIR. If your TIR is below where you and your doctor would like it to be, you can ask a few questions to possibly make any adjustments with your provider.
- Is my goal of %TIR right for my age/lifestyle/ability?
- Does my target range need to be adjusted?
- Has my nutrition/stress levels/physical activity changed recently?
- Is my water intake good?
- Have my medications changed recently?
Going over your TIR with your provider and asking these questions can help you make any necessary changes to your diabetes management to help you reach your goals.
The Association of Diabetes Care & Education Specialists (ADCES) provides the following guidelines regarding TIR range goals depending on age and pregnancy.
Keep in mind that these guidelines are designed to help you stay as healthy as possible while also minimizing your risk of severe hypoglycemia.
|Person with diabetes||Blood sugar range||Time-in-Range||Time-Below-Range||Time-Above-Range|
|Adults T1 & T2||Between 70-180 mg/dL||>70% (about 17 hours)||<5% (just over 1 hour)||<30% (about 7 hours)|
|High-risk for lows (children & elderly)||Between 70-180 mg/dL||>50% (about 12 hours)||<1% (about 15 minutes||<10% (about 2.5 hours)|
|Pregnancy with Type 1 diabetes||Between 63-140 mg/dL||>50% (about 12 hours)||<5% (just over 1 hour)||<25% (about 6 hours)|
|Pregnancy with Type 2 or Gestational diabetes||Between 63-140 mg/dL||>90% (about 21 hours)||n/a||n/a|
Diabetes is a very personalized chronic illness, meaning no two people have the same experiences with diabetes. Your goals for your target range, and how often you are within that range, should be personalized to you in consultation with your healthcare practitioner.
Editor’s note: Educational content related to time in range is made possible with support from Roche Diabetes Care, an active partner of Beyond Type 2 at the time of publication. Editorial control rests solely on Beyond Type 2.