Best Times to Test Your Blood Sugar

by Eileen Bailey Health Writer

Why should you test your blood sugar?

When you have diabetes, your blood sugar levels don’t always stay in an optimal range. Testing your blood sugar helps you understand how food, activity, and medicine affect your blood glucose, according to the American Diabetes Association. They suggest keeping a log, noting the date, time, and blood glucose level. You might also want to notate what you were doing or eating prior to testing your glucose levels.

Checking blood sugar in morning.

When should you check your blood sugar?

Many people check their glucose levels when they first wake up, before a meal, and two hours after eating. This helps them make decisions about food and diet that can help to keep blood sugar levels stable. There are other situations you encounter every day that may also affect your blood glucose. Keep reading to find out when you should check your blood sugar.

Checking insulin before lunch.

Before a meal and two hours after eating

Testing your glucose before a meal and two hours after eating helps you make good decisions about foods and medication, according to Kaiser Permanente. Testing before eating will tell you how much food to eat and how much medication you need. Testing several hours after you eat gives you information on whether you are taking enough medication to cover the food you eat during a meal.

Doctor handing patient new prescription.

If your diabetes medication changes

When your medication for diabetes changes or is adjusted, it’s important to know how that change is working. The best way is to check your blood sugar levels more often, according to Check your blood sugar levels before and after taking medication and keep track of the results to show your doctor.

Home care nurse explaining new medication to patient.

If you start, stop, or change any medications

Different medications can have an effect on your blood sugar, for example, steroids and anti-psychotic medications increase your blood sugar levels according to the American Diabetes Association. Several medications, such as beta-blockers, bactrim, MAO inhibitors, and metformin can cause low blood sugar according to MedLinePlus. Whenever you start, stop or change medication, it is a good idea to frequently test your blood sugar until you understand how the medication affects your glucose levels.

Checking blood sugar before starting day.

When you wake up

Some people experience high blood sugar levels in the morning. This is sometimes called the Dawn phenomenon and is a result of body changes that occur during sleep, according to the Cleveland Clinic. Testing your blood sugar when you wake up, including waking from a nap, will help you understand your body’s reaction and determine (with your doctor) whether your insulin schedule or dosage needs to be adjusted.

Getting comfortable to sleep.

Before going to sleep

Testing your blood sugar before going to sleep can help you avoid having a low blood sugar episode during the night. If your blood sugar levels are low at bedtime, eating a snack before you go to sleep can help alleviate a dip during the night.

Checking blood sugar before starting yoga.

Before and after exercise

Exercise and high activity levels can cause sudden changes in your blood sugar levels. Testing your blood glucose before and after exercise can help you take steps to keep your blood sugar level as close to normal as possible before, during, and after exercising, according to Kaiser Permanente.

Man sick in bed.

When you are sick

When you are sick, your blood sugar levels can run high even if you aren’t eating, according to When you aren’t feeling well, you should test your glucose more frequently than usual and make adjustments to your medications when necessary.

Low blood sugar reading and insulin pens.

Before driving a vehicle or operating machinery

Low blood sugar levels can cause fatigue, dizziness, cognitive difficulties, and loss of muscle coordination according to It can be dangerous to drive a motor vehicle or operate machinery with low blood sugar levels. Check your glucose to see if you need to eat a snack before driving.

High blood sugar check.

When you suspect hypoglycemia or hyperglycemia

If you are concerned about your blood glucose level, test them before making a correction. Some people try to make corrections based on how they feel rather than doing so based on actual readings. If you feel a hypoglycemic or hyperglycemic episode coming on, test first and then make the appropriate correction.

Stressed out foreman on job site.

When your stress increases

Stress, physical or emotional, can alter your blood glucose levels according to the American Diabetes Association. If you are going through a period of high stress, take the time to test your glucose more often than you typically do. When testing your glucose, rate your stress level between 1 and 10. After several weeks, you should be able to see a pattern and discern how stress affects your blood sugar and make corrections accordingly.

Eileen Bailey
Meet Our Writer
Eileen Bailey

Eileen Bailey is an award-winning author of six books on health and parenting topics and freelance writer specializing in health topics including ADHD, Anxiety, Sexual Health, Skin Care, Psoriasis and Skin Cancer. Her wish is to provide readers with relevant and practical information on health conditions to help them make informed decisions regarding their health care.