How to Keep a Blood Sugar Log (What to Write Down)

What to write down with each reading

A number on its own says little. The same 9.0 mmol/L (162 mg/dL) means something different before breakfast than two hours after a pasta dinner. Write down enough to explain the number later:

Date and time of day. Use fixed columns such as Before breakfast or Bedtime, so you do not have to write the time each time.
The reading, in the unit your meter shows.
Medicine taken at that time, if any: units of insulin, or a tick for tablets.
Food: grams of carbs if you count them, or a few words such as "porridge, banana".
Anything unusual: a workout, a stressful day, illness, alcohol, a late meal, poor sleep.
Lows and how you treated them, for example "3.4, 4 glucose tablets, 5.6 after 15 min".

Make it a habit

Most logs fail in the second week, not the first. These habits make it stick:

Keep the log next to your meter. If the paper is in a drawer, you will "fill it in later" and forget. A pocket card that folds into the meter case is always there when you test.
Write it down right after the test, before you put the meter away. It takes five seconds.
Use the same columns every day. When every reading has its own box, gaps are easy to see and the page stays readable.
Leave a box empty rather than guessing a number you did not measure.
Print a few weeks at a time, so a new page is ready when the old one is full.

Read your log once a week

Pick a fixed moment, for example Sunday evening, and look at the last seven days. You are looking for repeats, not single readings:

The same time of day running high or low. Mornings that are high most days point to something different from one high morning after a party.
The same meal followed by a high reading. If a certain breakfast is always followed by a spike, it shows up quickly on paper.
Lows after exercise, or at night.
How many days stayed in target. A simple mark for each in-target day turns the page into a quick score you can see from across the room.

Circle anything you want to ask about. If you use insulin and your diabetes team has taught you how to adjust your doses, these patterns are what you adjust from. If not, take them to your doctor or diabetes nurse rather than changing your treatment on your own.

Take it to your appointment

Bring the last few weeks, newest page on top. A page your doctor can scan in a minute, with notes next to the numbers, often leads to a better conversation than scrolling through a meter's memory. Write your questions on the back of the last page as they come up.

Paper, app or both?

Many meters and continuous glucose monitors store readings for you, and diabetes technology keeps getting better. A paper log still has a place: it shows two weeks at a glance, it holds the notes a meter cannot, and it works with any meter. Some people use a sensor for the numbers and a paper log for doses, food and notes. Use whatever you will actually keep up.

Not medical advice. This guide is general information. Your targets, testing times and treatment come from your doctor, diabetes nurse or clinic, who know your situation.

Make your logPick your testing times and units, then print it or save a PDF.

Questions

How long should I keep a blood sugar log?

Keep it as long as you test. If you only test now and then, a focused log for one or two weeks before an appointment is still useful.

Should I write down every reading?

Write down every reading you take. Leaving out the high or low ones makes the log look better but hides the patterns you are trying to find.

What if I forget to write a reading down?

Many meters store readings with a time. Copy it from the meter memory later. If you cannot, leave the box empty.

Do I need to write the time of each reading?

Not if your log has fixed columns such as Before breakfast and Bedtime. Write the time only for extra checks outside those columns.

How to keep a blood sugar log that is actually useful