Diabetes Dictionary

Terminology and jargon can be confusing so we have compiled a Diabetes Dictionary if you need to find out what something means. We hope you find this useful, and if there is something missing then do let us know and we can add it to the dictionary.


Artificial Pancreas (Closed Loop): This is currently only available via research studies with your diabetes team. It involves wearing an insulin pump and glucose sensor, and carrying a handset device similar to a smartphone. The sensor tells the device the glucose levels, which calculates the necessary insulin and tells the pump to deliver it. This constant messaging replaces the usual set basal rate in the pump. All meals and snacks need to be calculated for carbohydrate content and a bolus given in the usual way.

Autoimmunity: The process by which the body develops antibodies (like when fighting infection), but they are directed against some part of the body’s own tissues. In type 1 diabetes, the antibodies are against the beta (β) islet cells which make insulin, resulting over time the failure to make insulin and the diagnosis of type 1 diabetes.

Bolus Insulin: This refers to the insulin given as a single dose to cover carbohydrate containing foods or drinks (food bolus), or to correct if BG levels are high (correction bolus).

Basal Insulin: Everyone has a requirement for a background level of insulin in their blood. This is required to deal with the glucose released by the liver. In someone with diabetes, this is provided by long acting insulin such as Lantus, Levemir or Tresiba, or the basal rate of a pump. A pump only contains fast acting insulin, delivered in very small amounts over 24 hours.

Basal Bolus: This refers to combining fast acting bolus insulin (Novorapid, Humalog, Apidra) for meals and corrections, with a long acting basal insulin for those on injections, or continuous insulin for those on an insulin pump. If on injections, it can also be called multiple daily injections (MDI).

Blood Pressure/Hypertension: Blood pressure should be measured regularly when you attend clinic. It may increase in association with prolonged high glucose levels and may need treatment with tablets. It is rare in childhood. You can minimise risk of high blood pressure by keeping glucose in target, maintaining a healthy weight, keeping active and reducing the amount of salt in your food choices.

Carbohydrates (CHO): These are a food group which can also be called saccharides, which is Greek for sugar. Carbohydrates may be from starch (complex), natural sugar or added sugars. All carbohydrates are not the same as the rate at which they are absorbed from the gut varies enormously. Generally, simple sugars are absorbed quickly and complex carbohydrates containing fibre are absorbed more slowly. Some carbohydrate foods contain important nutrients for health, others do not.

Carbohydrate Counting: This is how you decide how much insulin to give with meals or snacks. By counting the grams of carbohydrate, you use your own insulin:carbohydrate ratio to calculate the dose. All insulin should be given before food.

Circadian Rhythm: Most hormones in the body are released in different amounts at different times over 24 hours. This is controlled by the natural day/night pattern and in part explains jet lag when you are flying across time zones and the circadian rhythm is disrupted. Due to the circadian rhythm of 2 hormones, cortisol and growth hormone, more insulin is needed in the early morning and late afternoon.

Continuous Glucose Monitoring Systems (CGMS): These are devices that are able to constantly measure glucose levels in the tissues by inserting a small probe under the skin. As it is not measuring blood glucose there is a small lag time, and so should be checked with a blood glucose in case of feeling hypo. There are alarms that can be set for high and low glucose levels. Some devices share information to pumps, others can share information via smartphones. There are specific criteria for these devices to be funded on the NHS.

Dawn phenomenon: This occurs particularly in growing teenagers. It refers to the natural circadian rise in blood glucose towards early morning, due to the release of growth hormone. This is why teenagers require high levels of insulin at night.

Diasend/Glooko: This is the system most clinics use to download most meters and insulin pumps. More than one device can be combined together to give a complete picture of glucose levels in table and graph displays. You can also download your devices at home using Diasend between clinic visits – ask your diabetes team how to do this.

Diabetic Ketoacidosis (DKA): This is a very serious condition that can be fatal if untreated. Symptoms include dehydration, fast breathing and vomiting. It is usually associated with high glucose levels but not always. Ketoacidosis refers to the build-up of ketones in the blood due to the breakdown of fat. Ketones are acidic and toxic to the body. Ketones are made if you have not had enough insulin, either by missing it or not giving sufficient doses regularly, or sometimes due to illness.

Fats: These are a calorie dense food group and source of energy. Healthy fats as found in oily fish, nuts, seeds, avocado, olive or rapeseed oil should be encouraged as they are heart protective. Less healthy fats are those found in processed foods. Too much fat of any type can lead to being overweight. Diabetes increases risk of heart disease at a young age, and young people will have their cholesterol measured from age 12 as part of annual review.

Glucose: A simple sugar which is absorbed through the gut very quickly and easily. It is the main food source for the brain and an essential energy source for the body. It is stored in the liver and muscles. Without diabetes, the blood glucose level is controlled very accurately between 4-7mmol/L. If blood glucose is high, glucose spills into urine and takes water with it resulting in passing large quantities of urine. This can also create thirst. Low glucose levels result in feelings of dizziness, hunger, shakiness and feeling weak (hypoglycaemia).

Glucagon: This is a natural hormone secreted by the alpha (α) islet cells of the pancreas, which is released when blood glucose levels drop too low. It causes the liver and muscles to release stored glucose to stop blood glucose levels falling too far. If you have T1 diabetes, this process is slower than in someone without diabetes.

GlucaGen ®: This is the trade name for artificially made glucagon and comes in an orange box. This is used to treat severe hypos if the person is unconscious, unable to swallow or take glucose by mouth.

Glycogen: Glucose is stored in the liver and muscles as a complex substance called glycogen. It is a source of glucose particularly when extra energy is required or if blood glucose levels drop too low. Glycogen is converted to glucose when stimulated by the glucagon released by the α islet cells of the pancreas or if you have given GlucaGen for a severe hypo. Glycogen stores only last about 12 hours if you do not eat and top them up.

Glycation: The HbA1c test is for glycated haemoglobin, and refers to the binding of glucose to proteins such as haemoglobin around the body. It measures how many red blood cells have glucose attached. Glucose binds to proteins in all tissues of the body and if glucose levels stay high for a long time, it can lead to irreversible changes to these proteins. It is the mechanism by which microvascular disease probably occurs.

Glycaemic Index (GI): This refers to how quickly glucose in the food is absorbed from the gut into the bloodstream. A high food is absorbed quickly, a low GI food is absorbed slowly. Naturally low GI foods are better for health (oats, wholegrains, beans, legumes, dairy foods, fruits) and can help reduce the glucose rise after meals. High GI foods (sugary cereals, white bread, mashed potato) raise glucose levels quickly and can be harder to match with insulin. If you are on a pump, different bolus options can be given to manage low GI food.

Glycaemic Load (GL): Glycaemic Load (or GL) combines both the quantity and quality of carbohydrates. The GL of food is a number that estimates how much the food will raise a person’s blood glucose level after eating it and is calculated by knowing both the amount of carbohydrate (in grams) and the GI of the food. It will not describe an exact rise in glucose, just whether the load is high, medium or low and therefore its predicted effect on glucose. A large amount of carbs of a low GI can have less effect than a smaller amount of a high GI food.

HbA1c (glycated haemoglobin): This term is often misunderstood; it is not a blood glucose level. It reflects blood glucose levels over a period of time, but is a measure of the number of red cells which have glucose attached. The ideal target for HbA1c is less than 48mmol/mol (also described as 6.5%) but this can be hard to achieve or maintain. As red cells last about 3 months before they are replaced by the body HbA1c reflects blood glucose levels over 2-3 months.

Hormone: This is a chemical which is made and stored in a particular part of the body (e.g insulin in the β cells of the pancreas, or thyroid hormone in the thyroid gland in the neck). When hormones are released they travel around all the body acting on all the tissues to do a specific job (e.g insulin transfers glucose from the blood into cells throughout the body).

Hypoglycaemia (hypo): This is the name for a low blood glucose level, usually defined as less than 3.9mmol/L. If it is associated with symptoms such as sweating, dizziness, feeling shaky, it is classed as a symptomatic hypo and needs quick treatment. It needs fast acting glucose to treat and a blood glucose recheck after 15 minutes. Common triggers for hypos are too much insulin for an amount of food, exercise and alcohol. Mild hypos are to be expected as part of good diabetes management, but should not be a frequent daily occurrence.

Hypoglycaemic Unawareness: This can occur in young children, if someone has frequent hypoglycaemia, or if they have diabetes of long duration. It means that they are less able or unable to detect hypoglycaemia at all, or until glucose levels are really low (less than 3mmol/L). If you think this is happening, discuss with your diabetes team.

Insulin: This is a hormone produced by the beta (β) islet cells of the pancreas. When glucose levels start to rise in the blood (after eating), insulin is released by these cells. Insulin allows glucose to move from the blood into muscles and cells to be stored around the body, maintaining the right amount of glucose in the blood between 4-7mmol/L. In T1 diabetes, this system does not work, and insulin must be given as an injection or via a pump.

Islet Cell: The Islet Cells (Islets of Langerhans) are found in small clumps throughout the pancreas. The beta (β) and alpha (α) cells are the ones most involved in diabetes. The β cells usually produce insulin in response to rising blood glucose levels. These are the cells which get destroyed in the autoimmune process of T1 diabetes and stop the body making insulin. The α cells usually produce glucagon in response to very low blood glucose levels, but this process can be impaired in T1 diabetes.

Insulin Pen: A device which delivers insulin by injection. Some are prefilled with insulin and are disposable, some contain a 3ml cartridge (300 units) which is replaced. Half and full unit pens are available.

Insulin Pump: This is another way of giving insulin. There are different brands available but they all deliver fast acting insulin via a small tube placed under the skin. A continuous basal rate is pre-programmed into the pump, but decisions have to be made around food and high glucose levels to give extra insulin when needed. When used properly they can help to manage diabetes very well and provide more flexibility than injections.

Insulin Resistance: This is seen more commonly in T2 diabetes, but is also relevant in T1. As you become older you require more insulin due to growth, but particularly during the rapid growth of puberty. During this time, growth hormone causes insulin resistance i.e insulin does not work as well as it has done previously and more insulin is required to have the same effect. This is shown by a changing insulin:carbohydrate ratio of 1 unit per 15g carbs in a 7 year old, but 1 unit per 5g carbs in a 13 year old for the same amount of carbs. If someone with T1 diabetes is overweight, this can also cause insulin resistance. Physical activity for teenagers (whether overweight or not) can help reduce insulin resistance.

Insulin Sensitivity (correction dose): This is the amount of insulin needed to bring a high blood glucose level back to target (5mmol/L). It varies depending on age, duration of diabetes and total daily dose of insulin.

Ketones: Ketones are made by the body as a result of breaking down fat as an energy source. This can be a normal occurrence overnight as no food is being eaten for many hours, and these are called starvation ketones. They disappear quickly when breakfast is eaten. In T1 diabetes, ketones might be produced at other times of day, and this is a sign that the body cannot use glucose as a fuel source due to lack of insulin allowing it to be transferred from the blood to the cells. Ketones are more likely during other illness such as a cold or infection. Ketones should be measured in the blood and anything over 0.6mmol needs treatment with extra insulin and fluids. Blood glucose and ketone levels must be checked more frequently to make sure the treatment is working. Ketones can be dangerous (see diabetic ketoacidosis).

Medtronic Carelink: This is another downloading system, specifically for Medtronic technology products which cannot use Diasend. It can also be used at home to download equipment between clinic visits.

Microvascular: This refers to the small blood vessels which are present throughout the body. They become damaged by high blood glucose levels and explain why the eyes and kidneys are at risk, if exposed to glucose due to poor diabetes management over several years.

Macrovascular: This refers to larger blood vessels, such as those around the heart. These are also at risk from high glucose levels, but also high fat levels in the blood. This is where cholesterol (a type of fat in the blood) can be deposited, causing narrowing of the blood vessels.

Nephropathy: This describes long term damage that can happen to kidneys. It starts with protein leaking from the blood via the kidneys into the urine. If this continues, the kidney’s ability to filter normal waste is reduced and kidney failure can occur. Early signs of nephropathy are high blood pressure and protein in the urine which is why both of these are checked regularly when you attend clinic. Risk of nephropathy can be reduced by keeping glucose levels as close to target as possible and providing a urine sample at least once a year (if over 12 years)  Blood pressure can be helped by eating less salt and exercising regularly.

Neuropathy: This is rare in childhood and is difficult to diagnose. It describes the long term damage done to the long nerves in the body leading to loss of sensation in toes and fingers. It may result in ulcers and skin damage. It can affect specific parts of the body such as the stomach (gastroparesis) associated with bloating and vomiting after eating. Keeping glucose as close to target as possible will help reduce the risk of neuropathy. Feet checks are carried out annually to help identify changes in sensation.

Pancreas: This is the gland in the body that produces insulin in someone without diabetes. It is found just behind the stomach. In T1 diabetes, although the beta (β) islet cells  for producing insulin are destroyed, the pancreas still has other important functions, like producing enzymes to help digest all the food groups.

Proteins: An important part of the diet for growth and repair. Protein foods include meat, fish, eggs, nuts, pulse vegetables (and their products) and milk products. If eaten in normal amounts, they have minimal effect on blood glucose. If large protein portions are eaten, it can cause a delayed rise in blood glucose.

Retinopathy: This describes the damage done to the blood vessels at the back of the eye, due to duration of diabetes or to poor management of diabetes. It is graded from 1-4 and refers to the macula and retina. The macula of the eye is used for fine vision so is very important. Grade 1 changes are not uncommon in young people but can be reversed with improved diabetes management. Risk of retinopathy can be reduced considerably by keeping blood glucose close to target and not smoking or being exposed to passive smoke. Annual screening from the age of 12 years can pick up any problems early.

Sensor Augmented Pump: This is an insulin pump that works in combination with a glucose sensor. If glucose levels are dropping, the sensor tells the pump to suspend insulin delivery to try and prevent a hypo. It restarts when glucose levels rise again. The next generation of this pump type will also respond to high glucose levels by automatically making basal adjustments. The high and low prevention functions should mean more time in glucose target.

Type 1 Diabetes: This used to be called insulin dependent diabetes mellitus, as insulin is required to treat this type of diabetes. At diagnosis, there is still some functioning of the beta (β) cells, but with time eventually no more insulin can be made and there is 100% dependence on injected or infused insulin from outside the body.

Type 2 Diabetes: This is the most common form of diabetes in the world, particularly in adults. In the early stages of the condition, lots of insulin is made, but it does not work well, so blood glucose levels rise. It is now starting to be seen in young people, usually those with a family history of T2 diabetes and those with an Asian or Afro Caribbean background. Being overweight and doing little physical activity also contribute to risk of T2 diabetes. Treatment for young people under 18y involves weight management, increased activity, and tablets to manage glucose levels. If this is not successful, insulin may have to be started.