What time of day is best to check blood sugar

Blood sugar readings provide insight into how your body is responding to your diabetes treatment plan. Understanding when to check your blood sugar can be done by following the testing schedule recommended by your healthcare team. Logging blood sugar levels helps you and your healthcare professional identify patterns of high and/or low blood sugars so that adjustments to your treatment plan can be made.

The Centers for Disease Control and Prevention (CDC) considers regular blood sugar testing the most important action you can take in managing type 1 and type 2 diabetes. Knowing when to check your blood sugar and how often depends on different health factors, including the type of diabetes you have. Always follow your healthcare team’s recommendations when it comes to deciding how often to test.

In this article, we outline suggested times to check your blood sugar, factors that influence testing frequency, testing tips, and more.

• When to test your blood sugar
• Factors that affect testing frequency
• Options to continuously monitor levels
• Testing tips

When to test your blood sugar

By talking with your healthcare team about your current health, age, level of activity, and other factors, you can determine how often you should be checking your blood sugar.

Depending on your unique needs, they may suggest testing blood sugar at any of the following times:

1. Before breakfast

Testing before you’ve had anything to eat or drink in the morning, also known as a fasting blood sugar, can let you know how well your body manages blood sugar while you sleep. It also gives you a baseline to see changes in your blood sugar throughout the day.

2. Before each meal

Checking blood sugar before meals tells people who inject insulin if they need to take a “correction dose” of insulin in addition to taking their bolus insulin to cover the meal.  When testing in pairs (pre-meal and post-meal), a pre-meal reading can act as a reference for how the food you eat and any pre-meal medications affect your glucose levels.

3. After each meal

The food you consume has a large effect on your blood sugar levels. The American Diabetes Association (ADA) recommends testing 1 to 2 hours after the start of a meal. To determine if your blood sugar level is where it should be, work with your healthcare professional to establish your target after-meal glucose range.

4. Before bedtime

A blood sugar reading taken before bedtime can tell you if your blood sugar is in a safe range, or if you need to have a snack before going to bed. It is also a point of reference for your morning blood sugar test, to compare and get a picture of how your blood sugar levels changed overnight.

5. In the middle of the night

For people with newly diagnosed type 1 diabetes, those at risk for severe hypoglycemia, or those who have other medical needs, testing during the night may be advised. Common times to test at night are right before bed, 2 hours after you fall asleep and at 3:00 a.m. It is important to keep a fast-acting carbohydrate snack, such as a small juice box, by your bedside in the event you need to treat a low blood sugar.

6. Before, during, and after physical activity

Physical activity can have varied effects on people depending on the intensity, duration, and type of exercise. Since exercise often lowers blood sugar, it is important to check your blood sugar before a workout and to have a snack if blood sugar is below your target to help prevent hypoglycemia. If you are having symptoms of hypoglycemia during a workout, stop, test, and treat accordingly. According to the ADA, blood sugar levels can be affected after exercise for up to 24 hours or more. Testing after physical activity can help you get familiar with how your body responds to particular activities, so you can plan accordingly. Remember, even cleaning the house or yard work counts as physical activity. These guidelines apply to those types of daily activities as well.

7. If you think your blood sugar might be too high, too low, or falling quickly

You can be more precise in treating a high or low blood sugar by understanding how your current blood sugar level correlates to your symptoms, and determining the appropriate treatment. Symptoms can vary from mild to severe, so the only way to truly know your blood sugar level is to test if you have a meter or continuous glucose monitor handy.

8. When you’re sick or stressed

Balancing food, medication, and physical activity to keep blood sugar in range can be difficult. Additional factors such as stress, illness, and pain can also raise blood sugar.  Testing more often during times of illness or stress may be recommended by your healthcare professional as well as testing for ketones if blood sugar levels become very high.

9. When using insulin

For people using an insulin pump or insulin injections throughout the day, the ADA recommends testing multiple times daily. If you take another kind of medication, test your blood sugar level as often as your healthcare team recommends.

Testing frequently and recording your results in a printable logbook or app allows you to observe trends. If you notice an out-of-range result that occurs at the same time of day for several days in a row, take a closer look to see if there is a common factor that may be the cause. Your healthcare professional or diabetes educator can help you identify these patterns and offer a plan to bring readings closer to your target range.

Factors that affect testing frequency

You may be wondering when to check your blood sugar based on the type of diabetes you have or the medications you take. Testing schedules are different for each person based on their type of diabetes, medications, lifestyle, and other factors.

Diabetes type

For those with type 1 diabetes, the pancreas can no longer make insulin to regulate blood sugar so levels will vary depending on food intake (particularly carbohydrate), insulin doses, activity levels, and more.

The ADA recommends a blood sugar testing frequency that helps people with type 1 to meet their specific needs and goals, including:

• Prior to meals and snacks
• At bedtime
• After meals (on occasion)
• Prior to exercise
• When low blood sugar is suspected
• Following a low blood sugar until stable
• Prior to tasks that are critical, such as driving

People with type 2 diabetes who take insulin or certain glucose lowering medications may need to test multiple times per day. Since insulin and other diabetes medications like sulfonylureas or meglitinides can increase your chances of hypoglycemia, testing more often may be recommended to help prevent a severe low blood sugar.

A treatment plan for someone with gestational diabetes may include testing in the morning, before and after meals, and at bedtime for women who take insulin injections during their pregnancy. Women who manage gestational diabetes with meal planning alone will test blood sugar according to their healthcare professional’s recommendations. Physical activity is recommended, and your healthcare team may advise that you test around activity as well. Once diagnosed, your healthcare team will work with you to setup a testing plan that is specific to your needs.

Medications

As discussed above, taking insulin whether through injections or an insulin pump, requires more frequent testing to closely monitor blood sugar levels. The American Association of Clinical Endocrinologists (AACE) recommends insulin users to test blood sugar 4 times daily and before taking insulin. The ADA offers similar recommendations, with increased testing frequency suggested for those at risk of frequent hypoglycemia, when experiencing symptoms of out-of-range blood sugar, or to better meet target goals.

Testing frequency for people who take oral medications, especially those that have potential for hypoglycemia risk, should be personalized by your healthcare professional. Your healthcare professional can determine the needed changes in your medications by using pattern management. This involves looking for patterns in your blood sugar readings. Checking frequently, such as while fasting (first thing in the morning) and 1-2 hours after a meal as well as any other times, will provide enough data to form patterns.

If you do not take medication to manage your diabetes, you may not need to test as frequently. However, testing more often can provide these benefits:

• Better glucose control
• Learn your body’s response to certain foods and portion sizes
• Identify blood sugar patterns
• Gain confidence in your diabetes management

Options to continuously monitor glucose levels

A continuous glucose monitor (CGM) measures glucose levels at regular intervals throughout the day through a small sensor under the skin. These devices include various features like current glucose readings, high and low glucose alerts, and charts for viewing glucose trends. This can be a helpful diabetes management tool for individuals who need to test multiple times a day, as it can take the worry out of remembering when to check blood sugar levels.

Using a CGM can create awareness for your current and projected blood sugar levels, viewed conveniently on a smartphone or receiver, without pricking your finger. If you have an out-of-range result, having the reading handy can allow you to act faster to treat a high or low. Many CGMs or flash glucose monitors (FGM) provide a trend arrow next to the reading to indicate whether your glucose is currently rising, falling, or remaining steady.

Some CGMs have alerts that will notify you when you are heading toward or currently have a low or high glucose level. These notifications may help ease your worry about remembering when to check your blood sugar so you can focus on your daily activities.

Testing tips

Practice good testing habits

Accurate blood glucose readings are important for insulin and medication dosing, avoiding highs and lows, physical activity, and overall health. When testing, there are many factors that can affect the accuracy of your results, such as temperature or storage conditions, substances on your hands, and more. If you have a reading that does not match how you feel, wash your hands under warm water and repeat the test. You can also check if your meter and strips are working properly by performing a control solution test. Make sure to use the compatible control solution, as indicated in your meter owner’s guide.

Schedule reminders

If you have trouble remembering when to test or if you simply want to put it at the back of your mind, some diabetes apps like the AgaMatrix Diabetes Manager allow you to program custom time and event-based reminders. An app can also be useful for tracking glucose, insulin, carb, and weight data in one place.

Plan ahead

Sometimes your daily activities might dictate when meals are planned, and they may not always align with your usual testing schedule. Since blood sugar testing and insulin doses often revolve around mealtimes, it is important to have a backup plan in case lunch or dinner times are unpredictable.

Always check your blood sugar if you are feeling low. Knowing your number before treating low blood sugar is important since some people can feel symptoms of low blood sugar when it is high. Always carry a rapid acting carbohydrate snack in case a corrective action is needed  to treat a low blood sugar.

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Checking and tracking your blood sugar at the times and frequency your healthcare professional advises is vital to your diabetes care and overall health. If you have questions specific to your situation about when to check your blood sugar, don’t be afraid to discuss this with your healthcare professional. You can also ask for a referral to a Certified Diabetes Care and Education Specialist, who can personalize a testing schedule for your needs.

There are also many resources, tools, testing, and tracking methods to simplify the process. Find what works best for you and practice making it a habit, and you’ll be on your way to better blood glucose control.

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Reviewed by: Melissa Herrmann Dierks , RDN, LDN, CDCES

Melissa Herrmann Dierks RDN, LDN, CDCES is a Registered Dietitian Nutritionist, Certified Diabetes Care and Education Specialist, and Licensed Dietitian Nutritionist in Huntersville, NC with over twenty-five years of professional experience in the field of nutrition and diabetes education. In addition to providing nutrition solutions for adults and children, she provides nutrition communication services to the food and beverage industry and is the owner of Supermarket Savvy. Melissa has held various sales and marketing positions for leading companies in the diabetes space including insulin pump, blood glucose monitor, and diabetes supply distribution companies.

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