Diabetes mellitus is a metabolic disease that is characterized by chronic elevated blood glucose levels (hyperglycemia). Therefore, the main goal of diabetes management is to keep blood glucose levels within normal limits or a target range as much as possible. If diabetes is not well controlled, further challenges to health may occur. People with diabetes can measure blood sugar by various methods, such as with a glucose meter or a continuous glucose monitor, which monitors over several days. Glucose can also be measured by analysis of a routine blood sample. In addition to lifestyle modification, some individuals may need medications to adequately control their blood sugar levels. Other goals of diabetes management are prevention or treatment of complications that can result from the disease itself and from its treatment.

Diabetes is a well known chronic disease that affects many individuals of all ages worldwide. There are many subtypes including Type 1, Type 2, gestational diabetes, maturity-onset diabetes of the young (MODY), neonatal diabetes, etc., with Type 1 and Type 2 being the most common. It is important to have control of this condition as uncontrolled diabetes can cause many complications. Diabetes can cause acute problems such blood sugar that is too low (hypoglycemia) or too high (hyperglycemia) which can cause acute symptoms. Diabetes also affects the blood vessels in the body, which are the routes blood take to deliver nutrients and oxygen to the organs in the body. By affecting the blood flow, diabetes increases the risk of other conditions such as strokes and heart disease (heart attacks). Diabetes is also associated with microvascular affects (small blood vessels) in organs such as the eyes and the kidneys and can cause diabetic retinopathy and diabetic nephropathy, respectively.

In addition to maintaining adequate blood sugar levels in the body, control of other risk factors that contribute to complications such as smoking, alcohol use, excessive weight, high blood pressure, and high cholesterol are also very important. Often, the recommended treatment for diabetes mellitus is a combination of lifestyle changes such as increasing exercise and healthy eating, along with medications to help control the blood glucose levels in the long term. In addition to management of the diabetes, it is recommended to have routine follow up with a primary care physician or endocrinologist as well a variety of specialists to assist in managing possible common complications such as foot ulcers, vision changes, and hearing loss.

There are several methods in which blood sugar is measured including with a glucose meter, continuous glucose monitor (CGM), and routine bloodwork.

The glucose meter, also known as a glucometer, is a common and simple method using a portable electronic device to measure glucose levels either at home or in a clinical setting. The glucose meter works by taking a small sample of blood using a lancet (a sterile pointed needle) to prick a fingertip, usually the index or middle finger (Image 1). The blood droplet is usually collected at the bottom of a test strip, while the other end is inserted in the glucose meter. The drop of blood is drawn into the meter and can directly measure the glucose in the sample. The units of blood sugar level from a glucose meter, will result in either mg/dL (milligrams per deciliter in the US) or mmol/L (millimoles per liter in Canada and Eastern Europe) of blood. Proper user technique and environmental conditions are important in obtaining reliable readings and accurate glucose measurements. Control of diabetes may be improved using home glucose meters to regularly measure glucose levels as this method provides rapid results allowing individuals to make timely decisions regarding diet, exercise, and medication.

Continuous glucose monitors (CGMs) are another method to measure blood glucose levels and is widely used among individuals with diabetes. A continuous glucose monitor is a device that sits on the surface of the skin (usually on the arm or abdomen) and measures the amount of glucose between the cells with a probe. The device does not directly measure the blood sugar but rather tracks the interstitial glucose levels which are similar to blood glucose levels. The other part of the CGM, known as the transmitter, then sends the information to a receiver, an insulin pump, or a compatible smart device. Unlike the traditional glucose meter, CGMs will report the glucose level continuously and has an alarm that will alert the person if the glucose level is too high or low, helping to prevent emergencies. The device is able to graph the glucose readings over the time the sensor was in use and track trends. This allows for timely adjustment of diet, activity levels, medications, and/or illness In addition, the information from the CGM can be downloaded and sent to a second person (such as a parent, caregiver, or partner) or physician for their review. CGMs have also been shown to improve glycemic control, reduce Hb A1c levels, and/or reduce the risk of hypoglycemic events. They also can reduce the need for multiple fingersticks throughout the day, which may be preferred by some individuals. Popular CGM devices include Dexcom, Freestyle Libre, and Medtronic.

In addition to the above tests, glucose can be measured on routine labs. One common test ordered by healthcare providers is a Basic Metabolic Panel which is a blood test that looks at several different substances in the body, including blood glucose. Usually, individuals are told to fast for 8 hours before drawing the labs so that the provider can see the fasting glucose level. The normal range for fasting blood sugar in people without diabetes is 70 to 99 mg/dL (3.9 to 5.5 mmol/L). The range for individuals considered to have prediabetes is 100 to 125 mg/dL (5.6 to 6.9 mmol/L). If the fasting blood sugar is greater than 126 mg/dL (7.0 mmol/L) on blood tests taken on separate occasions, individuals are considered to have diabetes.

Another useful test that is usually done via a blood test is the measurement of blood HbA1c (hemoglobin A1c) levels. In the blood, there is a molecule called hemoglobin which carries oxygen to the cells. Glucose can attach itself to this molecule and if the blood glucose is consistently high, the value of the A1c will increase. This test, unlike the other tests, is measured as a percentage because the test measures the proportion of all the hemoglobin that has glucose attached. This test measures the average amount of blood sugar control over a period of about 3 months (90 days). In people without diabetes, the HbA1c level ranges from 4.0 to 5.7%. The range for people with prediabetes is 5.7 to 6.4%, and anything above 6.4% is considered diabetic range. Due to the HbA1c serving as a accurate indicator of overall glycemic control, regular 6 month laboratory testing of HbA1c (glycated hemoglobin) is recommended to gauge long-term control and allows for more information to then adjust a person's lifestyle as well as routine medication dosages in such cases.