How to Check Your Blood Sugar Levels (and Why Monitoring Is Important)
Takeaways
Blood sugar monitoring helps maximize time spent in your target range, preventing long-term health problems and improving mental wellbeing.
Testing frequency differs on an individual basis—and is dependent on the type of diabetes you have, your treatment plan, and how well controlled your condition is.
You can check your blood sugar level at home using either a glucometer (blood sugar meter) or a continuous glucose monitor (CGM).
Compared to CGMs, glucometers are typically friendlier on the wallet and suitable for all conditions and patients (CGMs may not be indicated in those undergoing dialysis).
On the other hand, CGMs are advantageous over glucometers as they use a sensor inserted under the skin to measure glucose readings every few minutes, eliminating the inconvenience and pain of fingerpricks.
Your HbA1c—measured every 3 to 6 months at your regular check-ups with your doctor—tells you the average blood sugar level over 3 months. It serves as an indication of how well-controlled your diabetes is.
It’s important to keep your blood sugar levels in your target range as much as possible to help prevent or delay long-term, serious health problems, such as heart disease, vision loss, and kidney disease. Staying in your target range can also help improve your energy and mood. How do you know if your blood sugar levels are within range? That is where monitoring comes in.
Why test my blood sugar level?
Blood sugar testing provides useful information for diabetes management. It can help you:
Monitor the effect of diabetes medications on blood sugar levels
Identify blood sugar levels that are high or low
Track your progress in reaching your overall treatment goals
Learn how diet and exercise affect blood sugar levels
Understand how other factors, such as illness or stress, affect blood sugar levels
How can I check my blood sugar level at home?
You can use a glucometer (blood sugar meter) or a Continuous Glucose Monitor (CGM) to check your blood sugar.
A blood sugar meter measures the amount of sugar in blood from a fingerprick. To use it, you will need to prick your finger with a lancet, and squeeze blood from your finger onto a test strip, before the meter is able to read your blood sugar. You will need to repeat these steps each time you wish to measure your blood sugar. Read more about this here.
A CGM uses a sensor inserted under the skin to measure your blood sugar every few minutes eliminating the need for a fingerprick. Using a CGM also gives you and your doctor a more complete picture of your blood sugar including its response to various lifestyle factors and medication. This allows you and your doctor to rapidly optimize your management plan for better results. You can learn more about CGMs in this article.
Choosing between a glucometer or a continuous glucose monitor
Using either a glucometer or a CGM allows you to monitor your blood sugar level. Below are some of the considerations when choosing between the two options:
Glucometers are typically cheaper and are covered by government subsidies and insurance.
Glucometers are suitable for all conditions and patients (CGMs may not be indicated in certain populations, such as those that are undergoing dialysis or who are on certain medications).
CGMs provide a much richer insight into your blood sugar level given the continuous nature of the data. This allows you and your healthcare team to better monitor response to therapy and make adjustments.
CGMs are more convenient - there is no need to do finger pricks to measure your blood sugar level.
When and how often should I check my blood sugar level if I have diabetes?
The frequency of testing differs from person to person and is dependent on the type of diabetes you have, the medication you are on as well as how well controlled your condition is. When drawing up the treatment plan, frequency of monitoring should be part of the discussion that you have with your healthcare provider.
In general, if you have type 1 or type 2 diabetes and are on insulin (with multiple injections) or have gestational diabetes, you may be advised to test your blood sugars more frequently - four to ten times a day.
In other cases, you may not be asked to monitor your blood sugar on a daily basis. In these instances, you may be asked to measure your blood sugar on a “rotational” basis - for example, before and after breakfast on 1 day, before and after lunch on another day, before and after dinner on yet another day, so on and so forth. This decreases the frequency of testing, but still provides insight into your blood sugar levels. Importantly, measurements should be paired (before and after the same meal) so that they can be interpreted meaningfully.
When is the best time for checking my blood sugar?
There is no absolute “best time” for checking blood sugar levels. It really depends on the objective of measuring your blood sugar. e.g. Is it to evaluate the effectiveness of a medication, or it is to learn the effect of your diet? Typically, you may be asked to check your sugar levels:
When you wake up, before eating or drinking
Before and after each meal (typically two hours after the meal)
Before bed
Before and after exercise (typically in type 1 diabetes)
What are blood sugar targets?
A blood sugar target is the range that you should aim for as much as possible. The target range should be individualized depending on your goals, and should be decided with your doctor. Factors that could affect the targets include:
Type and severity of diabetes
Age
Duration of diabetes
Pregnancy status
The presence of diabetes complications
Overall health and the presence of other medical conditions
In general, the recommended blood sugar target ranges for continuous glucose monitoring are:
Those who are < 60 years old can aim for even lower glucose targets.
What is causing my blood sugars to be out of range?
Here are some common scenarios of blood sugars being out of range, possible reasons for them and what to do if you face these scenarios.
High glucose levels before breakfast
Morning glucose levels are often referred to as fasting glucose levels. If these levels are out of range, you may find that it is difficult to keep your levels down for the rest of the day. Possible reasons why your blood sugar is high in the morning include:
Consuming sweet drinks (coffee/tea with sugar, fruit juice) in the morning before measuring your sugar levels
Forgetting to take medication
What to do if your blood sugar is high in the morning:
If this is the first time you notice it happening or if it only happens occasionally, try taking note of what you had the night before and the duration of sleep you had
If your blood sugar has been high in the mornings continuously for a few days, speak to your healthcare team about it
High glucose levels before meals
If your levels are out of the target range before your meals, think about whether you had anything to eat or drink within the last two hours. If the answer is yes, your glucose levels may have been caused by this. Perhaps you had a chocolate bar on the way home, or a sweet drink before dinner? If you have not consumed any food or drink, and your glucose levels are high before your meals, speak with your healthcare team as you may need to adjust your medication.
High glucose levels after meals
If your glucose levels rise very quickly after your meals, take a look at your food intake immediately preceding the raised level. Possible reasons for raised glucose levels after eating include:
Consuming refined carbohydrates such as white rice or noodles, pastries or any other sugary foods
Consuming soft drinks or other sweetened drinks such as herbal tea with sugar added
Large portion sizes
Refined carbohydrates such as white rice and noodles are digested quickly and can cause your glucose levels to spike rapidly. In addition, carbohydrates in liquid form (such as soft drinks) are absorbed more quickly than those in solid form, as your body does not need to break them down. Sweetened drinks can therefore also cause your glucose levels to spike.
Choosing healthy complex carbs, such as whole vegetables, whole grains, beans and lentils, can prevent your glucose levels from swinging as they are less processed and your body needs more time to break them down. They also contain fibre which doesn’t convert into sugar. Eating soluble fibre can slow the absorption of sugar and improve your blood sugar levels. For example, drinking a glass of orange juice can increase your blood sugar rapidly as the orange has already been broken down. If you eat a whole orange instead, it will be broken down more slowly by the digestive system as it is high in fibre.
Make sure you also have sufficient protein (e.g. lean meats, beans, pulses) and healthy fats (e.g. salmon and tuna) in your meal, as these help to lower glucose spikes and keep you feeling full for longer.
Note that rapid glucose spikes and subsequent sharp drops can often leave people feeling lethargic, tired or have trouble concentrating – yet another reason to avoid foods which spike your blood sugar!
Hypoglycemia (Low Blood Sugar)
If you have any glucose levels below 4 mmol/L and you are not on medication that lowers glucose levels, you need not be concerned as your body is regulating itself.
If you are on medication which can cause low glucose levels, such as insulin or sulphonylureas (e.g. gliclazide or glipizide), speak to your healthcare team as some alterations may be needed.
What is HbA1c? Do I need to monitor my HbA1c too?
While a glucometer or CGM gives you the “at-the-moment” sugar level, HbA1c tells you the average blood sugar level over three months. This is typically measured every 3 - 6 months at your regular check-up with your doctor.
Why is it important to check your HbA1c regularly?
The HbA1c gives an indication of how well controlled your diabetes is. As your blood sugar level can fluctuate minute to minute, the HbA1c gives you and your doctor an idea of what your blood sugar level is “on average”. This allows you and your doctor to monitor the control of your diabetes at each review (based on your HbA1c, or your “average” blood sugar levels), and make adjustments to your treatment plan.
Lowering your HbA1c can bring long term benefits. Two large-scale studies – the UK Prospective Diabetes Study (UKPDS) and the Diabetes Control and Complications Trial (DCCT) – demonstrated that improving HbA1c by 1% (or 11 mmol/mol) for people with type 1 diabetes or type 2 diabetes cuts the risk of microvascular complications by 25%.
Microvascular complications include:
Retinopathy (eye disease)
Neuropathy (nerve damage)
Diabetic nephropathy (kidney disease)
Research has also shown that people with type 2 diabetes who reduce their HbA1c level by 1% are:
19% less likely to suffer cataracts
16% less likely to suffer heart failure
43% less likely to suffer amputation or death due to peripheral vascular disease
What should my HbA1c level be?
HbA1c targets should be individualized, and depends on the treatment goals, balancing the benefits of risk reduction of diabetes-related complications and the increased risk of adverse events due to low sugar levels, with tighter diabetes control.
For most individuals, a HbA1c target of ≤7.0% would be recommended. For individuals with short duration of diabetes, long life expectancy and no significant cardiovascular disease a HbA1c target of ≤6.5% should be considered.
How to Use a Blood Sugar Meter
There are different kinds of blood glucose meters, but most of them work the same way. Ask your health care team to show you the benefits of each. In addition, have someone else learn how to use your meter in case you’re sick and can’t check your blood sugar yourself.
Below are tips for how to use a glucose monitor:
Wash your hands with soap and warm water and dry well. Make sure there are no food particles or other substances on your hand as these can affect the reading.
Massage your hand to get blood into your finger.
Use a lancet to prick your finger.
Squeezing from the base of the finger, gently place a small amount of blood onto the test strip.
Place the strip in the meter.
After a few seconds, the reading will appear.
Track and record your results. Include details on food, activity, and medication where relevant.
Properly dispose the lancet and strip in a trash container.
Do not share blood sugar monitoring equipment, such as lancets, with anyone, even other family members.