Glycemia measurement is one of the most important practices performed in clinical assessment.
The main ways to measure the blood glucose level are described below:
- Fasting blood sugar or fasting glycemia – For this test, the blood sugar level is measured around 8 hours after fasting, usually after an overnight fast when the person has been sleeping.
- Post-prandial blood sugar – Here, the blood glucose level is assessed two hours after a meal is eaten.
- Oral glucose tolerance test (OGTT) – Here, several blood samples are taken at intervals after a glucose load is administered via mouth or injection. This test essentially provides an idea of the body’s capacity to handle a blood sugar load and reduce the level to normal.
- Glycated haemoglobin or HbA1c – This is a special test that measures long term blood sugar control. If the values are over 6.5, impaired blood sugar control at some point in the previous two or three months is assumed.
- Blood glucose can also be tested at any time of the day to give a random blood sugar result. A small portable device called a glucometer gives a blood sugar reading using just a small drop of blood taken from the finger tip. Random blood sugar is not usually a diagnostic test and is used to monitor glucose levels on a regular basis.
Normal blood glucose levels
- Fasting blood sugar – A normal fasting blood sugar level is between 70 and 100 mg/dl. Impaired fasting glucose is considered when the level is between 101 and 125mg/dl. Diabetes is suspected if the level is over 126mg/dl.
- A 2-hour post-prandial blood sugar level indicates diabetes if is over 200mg/dl.
Reviewed by Sally Robertson, BSc