Diabetes: how frequently should you check your blood sugar?

Diabetes: how frequently should you check your blood sugar?

Last Reviewed : 03/02/2021
Diabetes: how frequently should you check your blood sugar?


The need to test blood sugar/blood glucose is dependent on how the management of diabetes occurs. If this management is done with diet and exercise alone or with noninsulin medications, there is no need to test the blood sugar/glucose levels daily. On the other hand, if one takes insulin for the management of type II diabetes, there is a recommendation to test the blood sugar/glucose many times a day. This depends on the amount and type of insulin that is being used. These tests are to be usually done before meals and at bedtime if one is taking multiple daily injections. On the other hand, there is a need to test only before breakfast and dinner if there is the usage of either intermediate- or long-acting insulin. Patterns in the fluctuation of blood sugar (glucose) levels are observed in blood glucose monitoring, which occur in response to exercise, diet, medications, and pathological processes associated with blood glucose fluctuations.


Why test or check blood glucose or blood sugar?

Testing blood glucose or blood sugar levels help to:

  • Self monitors the levels in patients who take medications that can cause hypoglycemia or who might develop symptoms related to hypoglycemia.
  • SMBG (Self-Monitoring of Blood Glucose) is also recommended during periods of intermittent illness.
  • The frequency of SMBG is based on the glycemic targets as well as the treatments that are used.
  • CGM (Continuous Glucose Monitoring) is advised for patients treated with multiple daily insulin injections, particularly for those, with frequent hypoglycemia or hypoglycemic unawareness.
  • Patients, who take basal insulin, need to adjust the dose based on their glucose levels. They should test blood glucose/sugar levels at least once daily (fasting) and sometimes before dinner or bedtime (and even at other times when hypoglycemia is suspected).


To determine how often a check of the blood sugar/glucose levels is to be done, several factors such as current age, health, level of activity, and other factors play an important role. The healthcare team may suggest testing of blood glucose/sugar at any of the following times:

  • Before breakfast:

Fasting blood sugar is a test of blood sugar/glucose levels before one has had anything to eat or drink in the morning. It can suggest how well the body is managing the blood sugar/glucose levels while one sleeps. Additionally, this suggests a baseline for the changes that occur in the blood sugar throughout the day.


  • Before each meal:

If there is a need to take a 'correction dose' of insulin in addition to the bolus insulin (that covers the meal), it can be done by checking the blood sugar/glucose levels before meals. This test can be done as a pair of tests (i.e. pre-meal and post-meal). A pre-meal reading along with the medications is a reference for how the food being eaten affects the glucose levels.


  • After each meal:

Blood sugar levels are largely affected by the food that has been consumed. There is a recommendation for testing one to two hours after the start of a meal by the American Diabetes Association (ADA). For ascertaining the target after-meal glucose range and also for determining the exact level where one's blood sugar level is, it is necessary to work with the healthcare professional.


  • Before bedtime:

Whether the blood sugar/glucose is in a safe range can be achieved by taking a blood sugar/glucose reading before bedtime, which can also suggest a need to have a snack before going to bed. This is a reference point for the morning blood sugar/glucose test and also for comparison and receiving a picture of how the blood sugar/glucose levels changes overnight.


  • Middle of the night:

For people, who are at exposure to severe hypoglycemia or those, who have other medical needs, testing during the night is advised. The common times include: at night, right before bed, 2 hours after you fall asleep and at 3:00 A.M. In the event of treating low blood sugar, it is important to keep a fast-acting carbohydrate snack, like a small juice box, by the bedside.


  • Before, during, or after any physical activity:

The duration, intensity, and type of exercise i.e., physical activity, has varied effects on people. Exercise is known to lower blood sugar/glucose levels. So, before a workout, one needs to check the blood sugar and, if necessary, have a snack if the blood sugar is below the target levels. This helps to prevent hypoglycemia. In the event of hypoglycemia during a workout, stopping the workout, testing the blood sugar, and taking treatment is of utmost importance. ADA (American Diabetes Association) suggests that blood sugar levels are affected for up to 24 hours or more after exercise. One can plan in a better way if one tests after physical activities as it helps to keep a check on the way the body responds to these activities. ADA (American Diabetes Association) guidelines apply to daily activities, which even include cleaning the house or yard work.



  • If one's blood sugar is too high, too low, or falling quickly:

Understanding how the current blood sugar level correlates to the symptoms and determining appropriate treatments is a more precise way to treat high or low blood sugar/glucose levels. Symptoms can range from mild to severe, so the only way to actually know the blood sugar/glucose level is to have a glucose meter or continuous glucose monitor handy.



  • When one is either sick or stressed:

It is considered to be difficult to maintain blood glucose/sugar levels keeping in mind that one needs to balance food, medication, as well as physical activity. Illness, pain, and stress are some additional factors that influence an increase in blood glucose/sugar levels. Healthcare professionals often recommend testing of blood glucose/sugar levels when there are periods of illness and stress, and regular tests for ketones, in cases where the blood sugar levels are quite high.


  • When one uses insulin:

ADA (American Diabetes Association) has indicated testing multiple times a day, for those people who use either insulin injections or an insulin pump throughout the day. The healthcare team would recommend one to test the blood glucose/sugar levels more often, depending on any other kind of medication being taken.


Two important measures exist in the analysis of type II diabetes:


There is a requirement for capillary blood sampling and the use of a glucose meter when using a Self-Monitoring of Blood Glucose (SMBG) system. Examples of these systems are blood glucose meters and glucose strips. The blood glucose meters have to be approved by either the International Organization for Standardization or the US Food and Drug Administration (FDA). One needs to keep in mind that glucose meters measure the capillary blood glucose. Thus, most of the glucose meters provide plasma equivalent values rather than whole-blood glucose values. Glucose strips, on the other hand, need to be recalibrated to a meter every time a new batch is used. Due to this reason, there can be a batch-to-batch variation. Also, these strips are packaged in groups within a canister containing a desiccant that helps to control humidity. There is a possibility of patients forgetting to match the code on the strip bottle with the meter code. This could result in erroneous glucose value reading due to uncompensated batch variation. Newer meters have overcome this issue by automatically recognizing codes for strips.



To measure the glucose content of interstitial fluid (that correlates with plasma glucose), Continuous Glucose Monitoring (CGM) devices are used. The blood glucose readings are automatically transmitted to a device-specific receiver, smartphone, smartwatch, or other smart devices. As a matter of choice, a fluorescence-based sensor can be implanted subcutaneously by a health care professional. There are two main types of CGM systems: devices that require intermittent scanning and "real-time" devices. CGM plays an important role in detecting previously unrecognized hypoglycemia. Also, the real-time use of CGM can assist patients in injecting insulin more accurately for meals, thereby preventing hypoglycemia.


An insight into how the body responds to the diabetes treatment plan can be tracked from the blood sugar readings. One needs to follow the testing schedule given by the healthcare team to get a better understanding of when to check the blood sugar levels. Identification of patterns of high and/or low blood sugar levels is based on the blood sugar levels that are logged and using this information; adjustments can be made to the treatment plan. For the management of Type II diabetes, the Centers for Disease Control and Prevention (CDC) consider regular blood sugar/glucose testing to the most important action. Different health factors are involved in keeping track of when to check the blood glucose/sugar levels. The decisions on how often to test are always based on the recommendations from the healthcare team.



  1. The staff of Mayo Clinic Blood sugar testing: Why, when and how [Online] Mayo Foundation for Medical Education and Research https://www.mayoclinic.org/diseases-conditions/diabetes/in-depth/blood-sugar/art-20046628#:~:text=If%20you%20take%20insulin%20to,re%20taking%20multiple%20daily%20injections. [Updated on January 21, 2020]
  2. Thomas K. Mathew; Prasanna Tadi. Blood Glucose Monitoring [Online] StatPearls Publishing LLC https://www.ncbi.nlm.nih.gov/books/NBK555976/ [Updated on August 14, 2020]
  3. Melissa Herrmann Dierks , RDN, LDN, CDCES When to Check Your Blood Sugar  [Online] AgaMatrix, Inc.https://agamatrix.com/blog/when-to-check-blood-sugar/
  4. Healthline Media UK Ltd What to know about fasting blood sugar? [Online] Red Ventures Company https://www.medicalnewstoday.com/articles/nutrisystem-for-men-review

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