The Best Times of Day to Check Your Blood Sugar

One of the first things you should learn after being diagnosed with any type of diabetes is when to check your blood sugar. Your blood sugar levels change all the time during the day. These fluctuations can make living with diabetes difficult. 

Many everyday things can influence blood sugar levels, such as food, work, exercise, stress, pregnancy, medication, caffeine, intimacy and more.

If you’re new to managing diabetes, it can be tough to understand how these everyday things affect your blood sugar. You don’t have to figure it out alone. In this guide, we explain the best times to check your blood sugar with your blood glucose meter (BGM) or continuous glucose monitor (CGM) and why checking at these times can help you take better care of yourself.

Check your blood sugar as soon as you wake up

Check your blood sugar right after you wake up, before eating breakfast. This is called your fasting blood sugar level because you haven’t eaten anything for eight hours (give or take) while sleeping.

Regularly waking up with a high fasting blood sugar level in the morning could suggest:

• Your body may need more rapid-acting insulin for the meal you ate the evening before. Consider setting an alarm to check your blood sugar in the middle of the night to determine whether it’s actually high throughout the night or only closer to the morning. This is especially important if you only check your blood sugar with a BGM. A CGM should wake you up in the middle of the night if you have high blood sugar. Keep your alarms on while you sleep—no vibrate mode.
• Your body may need more basal (background) insulin overnight.
• You’re having dawn phenomenon—a natural increase in blood sugar levels that usually happens in the early morning, before or as you wake up. If you believe you are experiencing dawn phenomenon, you should chat with your healthcare team to determine how much insulin to take to keep your morning blood sugar steady.

Regularly waking up with a low fasting blood sugar level in the morning could suggest:

• Your body might need less rapid-acting insulin for the meal you had last night. But if that were true, your blood sugar would probably be low for many hours before you wake up in the morning. You might want to set an alarm to check your blood sugar during the night if you’re unsure when you’re going low. 
• Hypo unawareness—meaning you’re unable to feel your lows—is a serious, sometimes life-threatening challenge of living with diabetes. A low fasting blood sugar level could also suggest this. Setting an alarm to check your blood sugar levels can help you see whether it is low throughout the night or only in the morning. This is especially important if you only check your blood sugar with a BGM. A CGM should wake you up in the middle of the night if you go low. Always keep your CGM alerts loud while you sleep for this reason.
• Your body may be getting more basal insulin (background) than it needs during sleep.

If you’re experiencing any of the above-mentioned, talk to your health care team about changing your diabetes plan so you can reach your blood sugar goals and stop or reduce strange symptoms when you wake up.

Check your blood sugar before, during and after exercise

Checking your blood sugar around exercise is especially important for people who take insulin or other blood-sugar-lowering medications. Remember to always carry fast-acting carbohydrates with you while exercising, such as glucose gummies, powder or gels. Juice boxes and hard candies also come in handy!

It’s especially important to check your blood sugar levels before, during and after exercise if you’re new to diabetes or are new to exercising with diabetes. The more you study the way different types of exercise impact your blood sugar, the more you can develop a consistent plan around meals and exercise to prevent highs and lows.

Different types of exercise affect your blood sugar levels differently. Exercising with diabetes might require a little trial and error, but it’s worth figuring out—everyone needs to move their body. 

A low blood sugar level before, during or after exercising could suggest:

• Your body may need less rapid-acting insulin for the meal or snack you eat before exercising.
• Your body may need a basal adjustment if you use an insulin pump, programmed to start before you start exercising. Most insulin pumps let you set a temp-basal, which can temporarily increase or decrease your background insulin for a specific period.

A high blood sugar level during or after exercising can happen, too. Certain types of exercise—like weightlifting, spinning or sprinting—can trigger release of certain hormones that increase blood glucose. Although we all respond differently, many people find that if they take a small bolus of insulin before or during these anaerobic exercises, it can  decrease the chances of high blood sugar. 

Be sure you work with a certified diabetes care and education specialist (CDCES) and your healthcare provider to discuss an ideal plan for exercising effectively with diabetes.

Check your blood sugar two hours after eating a meal

Checking your blood sugar about two hours after you eat is very important. It shows you how your body responds to  certain foods…

A pattern of high blood sugar levels after eating could suggest:

• Your body may need more rapid-acting insulin 
• Timing of your insulin dose prior to meals may need to be adjusted 
• If you use an insulin pump, certain settings may need to be dialed in to better meet the needs of your body (like carb ratio, insulin sensitivity factor and/or active insulin time)

A pattern of low blood sugar level in the hours after eating could suggest:

• Your body may need less rapid-acting insulin for your last meal
• Timing of your insulin dose prior to meals may need to be adjusted 
• If you use an insulin pump, certain settings may need to be dialed in to better meet the needs of your body (like carb ratio, insulin sensitivity factor and/or active insulin time)

 Checking two hours after eating may seem tedious, but it is important for your awareness. This practice allows you to continuously improve your diabetes management throughout your health journey. In most cases a carb ratio adjustment does the trick, but talk to your healthcare provider before making any changes. 

Check your blood sugar right before bed

You’re about to sleep for (hopefully) eight hours. Those hours make up one-third of your day and affect your blood sugar levels. Sleep impacts your overall diabetes health, including your next A1c result and your ability to reach your target blood sugar range the next morning.

If you regularly experience high blood sugar level right before bed:

• Your body may need more rapid-acting insulin for your previous meal
• Your body may need more basal (background) insulin during that time of day—especially if you’ve been struggling all day long with high blood sugars

If you regularly experience low blood sugar level before bed or while you are sleeping:

• Your body may need less rapid-acting insulin with the meal you just ate
• Your body may need less basal (background) insulin during that time of day

Checking your blood sugar before bed is important for managing your diabetes. If you use a CGM, it can help you see if your levels are rising or falling. If you only use a BGM, checking before bedtime gives you a good idea of where your levels are. 

This simple step can help you get the restful sleep you need, which is crucial for staying healthy and feeling your best. Taking charge of your health by doing this can make a big difference!

Checking is important, but checking too much can be damaging

Experiencing a high or low blood sugar every now and then without a clear reason can happen. Try not to rush into making big changes right away and look at multiple days of blood sugar results instead to see if you notice any patterns. 

While checking your blood sugar levels at key times throughout the day is undoubtedly important, overchecking can lead to obsessive thoughts and patterns that hurt rather than help your overall diabetes management. Setting boundaries around your care means checking enough to survive and live the life you want with diabetes.

Always consult your healthcare team for any physical or mental concerns as you navigate diabetes. It’s a lot to take in. You can take it one step at a time, or in this case, one blood sugar check at a time.
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