Blog · Blood sugar
Time in range, explained simply
What 70% in range means in hours, the common targets, and why it can tell you more than your average.
The short version
- Time in range is the share of your day your blood sugar spends between 70 and 180 mg/dL (3.9 to 10.0 mmol/L).
- A common goal for adults with diabetes is more than 70%, which is about 17 hours a day.
- It also matters how much time you spend low: the goal is under 4% below 70 mg/dL.
- It shows things an average hides, like a day of big highs and lows that averages out to "fine".
What time in range means
Time in range (TIR) is a simple question: out of all your readings, how many were in the target zone? If you wear a CGM, that's hundreds of readings a day, so TIR becomes a clear picture of your day. It's usually shown as a percentage over the last 1 or 2 weeks.
The standard range, agreed by an international panel of diabetes experts in 2019, is 70 to 180 mg/dL (3.9 to 10.0 mmol/L).
What the percentages mean in hours
| Time in range | Hours a day in range |
|---|---|
| 50% | 12 hours |
| 60% | About 14 and a half hours |
| 70% | About 17 hours |
| 80% | About 19 hours |
| 90% | About 21 and a half hours |
Every 5% is about 1 hour 12 minutes a day. That's why doctors say even a 5% improvement is worth having.
The common targets
For most adults with type 1 or type 2 diabetes, the 2019 international consensus suggests:
| Zone | Goal | Roughly per day |
|---|---|---|
| In range, 70–180 mg/dL | More than 70% | More than 16 h 48 min |
| Below 70 mg/dL | Less than 4% | Less than 1 hour |
| Below 54 mg/dL | Less than 1% | Less than 15 minutes |
| Above 180 mg/dL | Less than 25% | Less than 6 hours |
| Above 250 mg/dL | Less than 5% | Less than 1 h 12 min |
Older adults or people at higher risk of lows often have a looser goal, such as more than 50% in range with very little time low. In pregnancy with type 1 diabetes the range is tighter, 63 to 140 mg/dL (3.5 to 7.8 mmol/L). Your care team will tell you which goal fits you.
Why it can tell you more than an average
Picture two people, both with an average blood sugar of 150 mg/dL.
- The first stays between 110 and 190 all day.
- The second swings from 50 to 280 and back.
Same average, very different days. The second person spends a lot of time out of range, including dangerous lows. Time in range shows that difference. A1C can't, because it's an average too. More on that in our piece on estimated A1C.
How to move your time in range
- Look at time below range first. Reducing lows is the safety priority, and fixing lows often reduces the rebound highs after them.
- Find your hardest time of day. Many people struggle most after breakfast or overnight. A daily pattern view makes this obvious.
- Find the meals that spike you. A few meals usually cause most of the time above range. Checking 2 hours after eating shows which ones.
- Swap, don't ban. Pairing carbs with protein and fibre, or picking some lower-carb meals, can flatten the rise.
- Bring the numbers to your appointment. Changes to insulin or medication are for you and your care team to decide together.
Without a CGM
Time in range was designed for CGM data. With a few finger-pricks a day, a percentage can still be worked out, but it reflects only the moments you checked. It's still useful for spotting trends if you check at similar times each day.
Where to see it
In T1dApp, Insights shows your time in range for the week, your average, your lows, your daily pattern and an estimated A1C, in plain words. If your CGM or meter writes to Apple Health, turn on Apple Health sync and the readings come in without typing.
Snap your meal, see the carbs
T1dApp gives you carbs, calories, protein and fat from a photo, and your likely blood sugar 2 hours later.
Sources
This article is general information, not medical advice. Your targets, doses and diet should be set with your doctor or diabetes care team.