When Is the Best Time to Check Your Blood Sugar?

Medically reviewed by Do-Eun Lee, MD

For people with diabetes, checking your blood sugar can help you to better manage your health condition. Blood sugar is exactly what it sounds like—a measure of the glucose (sugar) levels in your blood. How often you need to check your blood sugar varies based on your healthcare provider's recommendation, but if you’re on insulin it’s often best to check it right before meals, a couple of hours after meals, and before bed.

Those with diabetes typically have high blood sugar levels, but your blood sugar is also at risk of dropping, leading to hypoglycemia. Checking your blood sugar levels helps you learn how your body responds to different treatment interventions, like dietary changes, medication, or physical activity.

Why Is It Important to Check Your Blood Sugar?

If you have diabetes, checking your blood sugar is essential to understanding what affects your blood sugar and how. You can learn whether your blood sugar levels are well-regulated or if you’re often hyper- or hypoglycemic. Having a deeper understanding of how your blood sugar changes in response to certain amounts or types of foods can teach you what your body can or cannot tolerate. Additionally, other factors like stress or alcohol consumption may be overlooked.

Monitoring your blood sugar gives you feedback on how your diabetes management interventions are working, including medication. This is important not just for yourself, but for your healthcare providers to know whether to make adjustments to your treatment plan. They may adjust your medication dosage, including insulin, or offer different dietary recommendations if your blood sugars are outside of their goal range for you.

Unsure if you should be monitoring your blood sugar? Your healthcare provider will typically test your blood sugar to see if you have diabetes during routine lab work. If you don't have diabetes, they can help you determine if blood sugar monitoring is still a good choice for you.

How to Check Blood Sugar

There are a few ways to check your blood sugar: a blood glucose monitor, a continuous glucose monitor, and an A1C blood test. An A1C test is done every few months in a lab, whereas a blood glucose monitor or a CGM is used regularly at home.

Blood Glucose Monitor

A blood glucose monitor—also called a blood sugar meter, a glucometer, or a glucose meter—is a tried and true method for monitoring your blood sugar. It’s a small machine that measures your blood sugar using a small blood sample.

You use a fingerstick to draw a drop of blood from your finger and then place the blood on a test strip to be read by the blood glucose monitor. The monitor shows you your blood sugar level at that moment.

Continuous Glucose Monitor (CGM)

Continuous glucose monitors (CGMs) are an increasingly common alternative to a blood glucose monitor because they automatically check your blood sugar level every few minutes so you don’t have to manually prick your finger whenever you need a reading.

CGMs are very popular now because they are convenient. They have a little sensor that you input under your skin and leave on around the clock. It’s thanks to this sensor that you can get consistent readings of your blood sugars, usually every few minutes.

The other nice thing about CGMs is that they can connect to your smartphone for you to collect data on your blood sugars. You don’t have to record the information with pen and paper for your own records or to share it with your healthcare provider.

CGMs give you in-the-moment, in-depth data on your blood sugar levels and trends so you can take action to help normalize your blood sugars throughout the day. They can also alert you when your levels are out of normal range.

A1C Blood Test

The final method of testing blood sugars is through an A1C blood test. This type of test should be done in addition to either using a blood glucose monitor or a CGM as it’s only done about twice a year in your healthcare provider's office. It measures your average blood sugar for the past 2–3 months.

Your healthcare provider may perform this test if they think you are at risk of developing diabetes or prediabetes, or if you have prediabetes and they want to monitor its development.

When Is the Best Time to Check Your Blood Sugar?

While it’s best to defer to your healthcare provider's recommendations for when to check your blood sugar, there are certain times that are generally best. How often you need to check your blood sugar will depend on a few factors, including whether you’re on insulin, how well-controlled your diabetes is, and whether you are trying any new treatment methods.

Those with type 1 diabetes or those with type 2 diabetes who are taking insulin generally need to check their blood sugar at least four times a day—before each meal and before bed. Whereas if you have well-controlled type 2 diabetes and aren’t taking insulin, you may only need to check your blood sugar once in a while. If you recently had a change in your medication, or your diabetes is poorly controlled, then you will likely need to check it more often until you find a treatment plan that works for you.

Common times to check your blood sugar include:

• When you wake up: Checking your blood sugars when you wake up is a way of testing your fasting blood glucose level, which is your glucose level after a long period of not eating or drinking.

• Right before a meal: This helps you dose insulin properly if you take insulin. It can also help you assess how a meal affects your blood sugar if you check your blood sugar after the meal as well.

• Two hours after a meal: Since food—particularly carbohydrates—raises your blood sugar, checking your blood sugar after a meal helps you and your healthcare provider understand how your food choices impact your blood sugar. It can also help determine whether your medication or insulin regimen needs to be adjusted.

• When you experience signs of hyper- or hypoglycemia: Signs of hyperglycemia (high blood sugar) include feeling thirsty, tired, or weak, frequent urination, headaches, and blurred vision. Signs of hypoglycemia (low blood sugar) include shaking, sweating, nervousness or anxiety, dizziness, and hunger. If you experience these symptoms, checking your blood sugar can help you determine how far out of the normal range your blood sugars are so you can take action.

• Before and after exercise: Exercise often causes your blood sugar to drop, so checking your levels before and after helps you understand what kind of snack you may need and how different types of exercise affect your body.

Understanding Your Results

Your blood sugar result will be in the form of milligrams per deciliter (mg/dL). Your healthcare providers may set unique goals for you based on your medical history, age, disease progression, and more. According to the American Diabetes Association (ADA), the recommended ranges for blood sugar are:

• Before a meal: 80–130 mg/dL

• 1–2 hours after the start of your meal: less than 180 mg/dL

A1C is a measure of your average blood glucose level over the past three months expressed as a percentage. However, sometimes you will also receive an estimated average glucose (eAG) reading in the form of mg/dL. The recommended ranges, per the ADA, are:

• A1C: Less than 7%

• eAG: Less than 154 mg/dL

Related: How Is Type 2 Diabetes Diagnosed?

What to Do With the Results

Collecting your blood sugar results is especially important for you and your healthcare providers to understand how well your treatment plan is working for managing your diabetes.

When you receive your blood sugar results day-to-day, it can be helpful to reflect on what may have affected your results, such as what and how much you ate, your alcohol consumption, physical activity, sleep habits, stress levels, hydration status, medication dosage and timing, illness, and more. This can help you gain a more intimate understanding of how your behaviors or other factors outside of your control may be impacting your blood sugar.

Besides processing this information yourself, it’s important to collect the data to share with your healthcare providers during your appointments. This allows them to understand how well-controlled your blood sugar is so they can adjust your treatment plan as necessary.

Related: What to Do When Your Blood Sugar Is High

When to Contact a Healthcare Provider

It’s best to meet with your diabetes care team at regular intervals to check in on your diabetes management and make alterations to your treatment plan as necessary. During regular visits, you can inform your healthcare provider about your blood sugar levels so they can assess how well-controlled your diabetes is. You can also ask any questions you have about interpreting your results and their treatment recommendations.

If you experience symptoms of diabetic ketoacidosis (DKA), you should seek help from a medical professional immediately. DKA happens when your body breaks down fat for energy because your body isn’t moving glucose to your cells to use for energy. This causes your liver to produce ketones, which can cause your blood to become acidic. It’s most common in those with type 1 diabetes and is often how they end up getting diagnosed. Symptoms of DKA include:

• Decreased alertness

• Dehydration

• Dry skin and mouth

• Fruity-smelling breath

• Trouble breathing

• Nausea or vomiting

• Abdominal pain

• Confusion

• Extreme sleepiness or tiredness

A Quick Review

Checking your blood sugar is important to understand how your diabetes treatment plan is impacting your disease management. For those taking insulin, checking your blood sugar daily is likely necessary; whereas if you have well-controlled type 2 diabetes and aren’t taking insulin, you may not need to check it on a regular basis.

Most often, it’s best to check your blood sugar before and after meals and before bed, but it may also be beneficial to check it before and after exercise, when you wake up, and if you experience signs of hyper or hypoglycemia. If you’re unsure if, how, and when to check your blood sugar, speak with your healthcare provider for individualized guidance.

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