When to Check Blood Sugar With Type 2 Diabetes

There is no single best time to check blood sugar that applies to everyone with type 2 diabetes. How often you check, and when, depends on your treatment plan and on what your healthcare professional asks you to do. The CDC states it plainly: how often you check depends on the type of diabetes you have and whether you take diabetes medicines, and your doctor will tell you when and how often to check.

What this article can do is explain the checking times that authoritative sources describe as typical, why the context of a check matters, and how to record checks so the schedule your care team gave you actually turns into a useful record. It is not a testing schedule. Yours comes from your doctor, nurse or diabetes educator.

The short answer: it depends on your treatment plan

Three of the most trusted sources on this topic say the same thing in slightly different words:

• CDC: “Your doctor will tell you when and how often to check your blood sugar levels.”
• NIDDK: “Ask your health care team about the best way to check your blood glucose level and how often you should check it.”
• FDA: “Follow the recommendations of your health care provider about how often to test your glucose.”

The reason is not evasiveness. People with type 2 diabetes are treated very differently — lifestyle changes alone, oral medicines, injectable medicines, insulin, or combinations — and the value of a check at a given time depends on which of those applies to you and what your care team is trying to learn. The same reading can be essential for one person and uninformative for another.

Common times healthcare professionals ask people to check

The CDC lists the following as typical times to check blood sugar. Typical means “commonly requested”, not “required for you”.

• When you first wake up, before you eat or drink anything
• Before a meal
• Two hours after a meal
• At bedtime

Each of these captures a different moment in the day. A waking or fasting reading is taken after the overnight period without food. A before-meal reading shows where you are going into a meal. A reading about two hours after a meal shows where you are afterwards — the ADA and NIDDK both describe post-meal readings as taken roughly one to two hours after the meal begins, so start timing from the first bite, not the last. A bedtime reading closes the day.

Which of these your care team wants, and on which days, is a decision they make with you. Some people are asked to check at one time every day; others rotate through different times across the week; others check only around specific situations. All three are legitimate schedules when they come from your healthcare professional.

When people may be asked to check more often

The CDC notes that if you have type 2 diabetes and take insulin, or if you often have low blood sugar, your doctor may want you to check more often — for example before and after you are physically active. The ADA lists groups who may benefit from checking regularly, including people taking insulin, people who are pregnant, people having a hard time reaching their blood glucose targets, and people who have low blood glucose levels, especially without the usual warning signs.

The NIDDK adds that even if you do not use insulin, checking at home can help you and your health care team make changes to your meal plan, physical activity or medicines, and can help you understand how certain foods affect your glucose. Whether that applies to you, and how often, is again a conversation with your care team — it is listed here so you know the question is worth asking.

Why the time of a check matters for your log

Timing is not only about when to prick your finger; it is what makes a reading interpretable later. A single number without context tells your doctor very little. A number labelled “Tue 7:05 am, fasting” can be compared with the other fasting readings that week. The ADA suggests looking at your record for readings that are too high or too low several days in a row at about the same time of day, because that kind of pattern may be a reason to review the care plan. You can only see the pattern if the time and context were written down.

So whatever schedule you are given, record each check the same way: date, clock time, the reading with its unit, and which of the typical contexts it was — waking, before a meal, after a meal, bedtime — plus a short note if something was unusual. Our guide to keeping a blood sugar log goes through each field, and the 7-day log example shows what a week of labelled entries looks like.

Recording the checks your care team asked for

Once you have a schedule, the practical problem is sticking to it and capturing the result each time. Two tools help.

A paper log. The printable blood sugar log sheet has a weekly layout with columns for fasting, before and after each meal, and bedtime — the same contexts the CDC lists — so you tick off the checks you were asked to do and leave the rest blank. There is a header line for the target range your doctor gave you.

A logging app. DiabetLog is a record-keeping tool: it does not measure glucose and it does not tell you when to test. What it does is let you set reminders for the times in your schedule, tag each reading with the time of day and a context such as fasting, chart the results against the target range you enter, and — for Premium users — export the history as a PDF report for your appointment. Readings are stored only on your device.

If your meter or a relative's report shows a different unit from the one you log in, convert it before writing it down with the mmol/L to mg/dL converter so all your entries stay comparable.

Questions to bring to your healthcare professional

The CDC suggests keeping these questions in mind for your next visit. They are the right way to turn “when should I check?” into an answer that is actually about you.

• What is my target blood sugar range?
• How often should I check my blood sugar?
• What do these blood sugar numbers mean?
• How can I improve or maintain my blood sugar levels?

Bring your log to that conversation. A few weeks of labelled readings make the “how often” question far easier for your care team to answer than a blank slate.

Follow the testing schedule recommended by your healthcare professional. Use this article to understand the vocabulary and to record your checks well — not to set your own schedule.