What is a blood sugar/glucose test?
A blood sugar/glucose test, as the name implies, measures the amount of sugar/glucose present in the blood at a particular time. Being a quantitative test, the results will tell you the exact amount of glucose (sugar) present in the blood sample you give.
When screening for blood sugar related conditions such as diabetes, hyperglycaemia (high blood sugar) or hypoglycaemia (low blood sugar), your doctor will usually order a random blood sugar test or fasting blood glucose (FBG) test or a glycosylated haemoglobin (HbA1c or haemoglobin A1c) test. All of these tests involve a blood draw.
Blood sugar testing can also be conducted on-site by a healthcare professional or done at home (particularly for those who are diabetic) using a glucometer (glucose meter). This device measures the amount of glucose (sugar) in your blood2, this is also known as glycemia (presence of glucose in the blood).
Why should I have a blood sugar test?
A doctor will request that you have a blood sugar test if he/she suspects you may have diabetes, low blood sugar (hypoglycaemia) or high blood sugar (hyperglycaemia). A blood sugar level test will first be used in the diagnosis of these conditions, after which the test will be used for monitoring. It is wise to have fasting glucose measured every year or two to screen for diabetes, especially if you are overweight, have a family history of the condition, suffer from hypertension (high blood pressure) or are a smoker.
If you have already been diagnosed as a diabetic, then you will need to have this test done regularly in order for your blood glucose levels to be measured and monitored on an ongoing basis. Your doctor will use the results to pick up on any severely low or high glucose levels, get an idea of how your exercise and diet are affecting your blood sugar levels and to make any necessary adjustments to your treatment plan.
How often should I test my blood glucose?
If you are not diabetic, then you may only have to have a glucose test conducted when your doctor recommends it. However, if you suffer from type 1 diabetes you may be required to test yourself several times every day. If you have diabetes type 2, then you may also have to test yourself a few times a day. The section that follows explains what your blood sugar levels should be (target ranges) in terms of diabetes type 1 and type 2:
Testing blood sugar levels with type 1 diabetes
How often to test
The National Institute for Health and Care Excellence (NICE) recommends that if you have type 1 diabetes you should test your blood sugar (glucose) no less than four times a day, this includes before every meal and going to bed.
To ensure that you test your blood glucose at regular times, your doctor is likely to recommend that you test at the below times:
- Before, during and after exercising
- Before driving and every two hours during longer drives
- Test more regularly when you are sick or ill
- When planning pregnancy, during pregnancy and breastfeeding
- If you do not reach your target levels of HbA1c of 48 mmol/mol
- If you are taking part in any high-risk activities such as sky-diving etc.
- If you experience regular hypos (hypoglycaemia – low blood sugar levels)
Should you be on a medication that may increase your risk of hypoglycaemia, then your blood sugar levels should be tested regularly. These include:
- All types of insulin
Target blood sugar levels
Your blood sugar levels are given to you as a unit of measurement written as either 'mmol/l' or 'mmol/litre'. In order for your risk of any long-term health issues due to uncontrolled fluctuations of your blood sugar levels to be minimised, your doctor will advise you to aim for the below target levels:
- Before breakfast = Your fasting level should be between 5 and 7 mmol/litre
- Before other meals during the day = Your level should be between 4 and 7 mmol/litre
Should you test your levels after eating, then the target should be between 5 and 9 mmol/litre when taken 90 minutes after your meal.
Your doctor will inform you about what your target levels should be, including what you should aim for before going to bed, this will depend on your dose of insulin and when you had your last meal.
Testing blood sugar levels with type 2 diabetes
How often to test blood sugar levels
How often you test your blood sugar levels if you have diabetes type 2 will depend on your personal health and condition, as well as if you are taking any medications.
If you are taking several insulin injections on a daily basis or are on an insulin pump, then your doctor is likely to suggest that you test yourself as often as those who have type 1 diabetes (four times daily).
Should you be taking medication that can cause hypoglycaemia, then it is advised that you should, at the very least, test your blood sugar levels if you notice any signs of low blood sugar (i.e. excessive perspiration, weakness or shakiness, nausea, hunger, headache, dizziness, blurred vision, anxiety, elevated heart rate or feeling faint).
Some medications that may cause hypoglycaemia in type 2 diabetics include:
- All types of insulin
- Prandial glucose regulators (nateglinide, repaglinide)
- Sulphonylureas (glimepiride, tolbutamide, glipizide, glibenclamide, gliclazide)
If you have diabetes type 2 and are not taking any of the medications listed above, then your doctor may inform you that there is less of a necessity to test your blood sugar levels, however, regular testing is often beneficial in monitoring your condition in any case.
If you are pregnant, planning on conceiving or breastfeeding, then your doctor may also recommend more routine testing.
Your doctor is likely to consider educating you on more routine testing should you fall into any of the above categories.
Testing your blood sugar levels is particularly helpful if you are someone with type 2 diabetes as you can then determine how activities and meals affect your blood sugar levels.
HbA1c measurement and targets for type 2 diabetes
**My Med Memo - HbA1c, is the abbreviation of Haemoglobin A1c, which is a form of haemoglobin, a pigment in the blood responsible for transporting oxygen in the body that glucose binds to (as glucose builds up in the blood it will bind to the haemoglobin in the red blood cells).
Measurement
If you are an adult with type 2 diabetes, then you will need to measure your HbA1c levels according to the below intervals:
- Until your HbA1c levels are stable and you are on a therapy that will not change, you will need to test these levels every three to six months, however, your doctor will recommend amount of time required between intervals according to your individual situation.
- Once your HbA1c levels and your blood glucose levels begin to stabilise as a result of therapy, then you are likely to only have to test yourself every six months.
Is it possible to test my blood sugar levels too few times?
Depending on the type of diabetes and the treatment you are undergoing for it, it is sometimes possible to test your blood sugar levels too seldom. For example, if you have type 1 diabetes and you are testing your levels less than the recommended four times a day, then you are likely to find your condition a difficult one to understand and manage as your blood sugar levels may seem to be more out of your control when you are not monitoring these more routinely and picking up on patterns of fluctuation that routinely occur.
If you struggle to test yourself as often as required, this may be linked to denial about your condition or other psychological issues such as depression or burnout.
If you feel as though you are having trouble coming to terms with your diabetes, then speak to your doctor or a mental health professional such as therapist to learn about coping techniques in order to get your disease under control and help wrap your head around it.
If you are on specific medication that may cause low blood sugar, then some countries will, by law, enforce that you test your blood glucose levels before driving and at least every two hours during longer journeys. Should you fail to do this, then your hypoglycaemia may lead to road accidents, putting your life and others at risk. Low blood sugar can also cause light-headedness, heart palpitations and anxiety – a dangerous combination when driving.
How do I take a blood sugar level test?
When a doctor recommends a blood glucose test, he/she or a nurse will draw blood from a vein in your arm and send it to a lab for analysis.
If this is done using a glucometer, this device will come supplied with a logbook, test strips and tiny needles or lancets. If your doctor is conducting this test, then the finger he or she plans to prick will be wiped with an alcohol prep pad. Your finger will then be pricked slightly with a small needle and gently squeezed in order to get a small drop of blood to form. The blood will then be placed on the strip provided and inserted into the glucometer. The device will process the data and show your glucose results on the screen. If you are diabetic, then you will conduct this test yourself in order to ensure that your diabetes is under control.
Regardless of the method used to measure your blood sugar level, your doctor will inform you of the results and discuss what they mean as well as any necessary treatment options with you.
References
2. FDA. Blood Glucose Monitoring Devices. Available: https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/InVitroDiagnostics/GlucoseTestingDevices/default.htm [Accessed 03.10.2017]