Diabetes glossary
Plain-language definitions for 52+ diabetes terms — A1C, CGM, DKA, insulin types, and more. Bookmark it as a quick reference.
A
- A1C (HbA1c)
A blood test measuring the percentage of hemoglobin with attached glucose, reflecting average blood sugar over the past 2–3 months. Normal: below 5.7%; Prediabetes: 5.7–6.4%; Diabetes: 6.5% or above on two tests.
See also: eAG (Estimated Average Glucose), Prediabetes, Diabetes
- Autoimmune diabetes
Diabetes caused by the immune system attacking insulin-producing beta cells. Includes Type 1 diabetes and LADA.
See also: Type 1 diabetes, LADA (Latent Autoimmune Diabetes in Adults), Beta cells
B
- Basal insulin
Long-acting insulin providing a steady background level throughout the day. Examples: glargine (Lantus, Toujeo), detemir (Levemir), degludec (Tresiba).
See also: Bolus insulin, Insulin, Insulin pump
- Beta cells
Insulin-producing cells in the pancreatic islets of Langerhans. Destroyed by the immune system in Type 1 diabetes.
See also: Insulin, Type 1 diabetes, Autoimmune diabetes
- Blood glucose
The concentration of glucose in the blood. Measured in mg/dL (US) or mmol/L (most other countries). Also called blood sugar.
See also: Glucose, mg/dL, mmol/L, Hyperglycemia, Hypoglycemia
- Bolus insulin
Rapid-acting insulin taken at mealtimes to cover carbohydrates and correct elevated blood sugar. Examples: lispro (Humalog), aspart (NovoLog), glulisine (Apidra).
See also: Basal insulin, Rapid-acting insulin, Correction dose
C
- Carbohydrate counting
A meal-planning technique for diabetes that involves tracking grams of carbohydrates to manage post-meal blood sugar spikes.
See also: Bolus insulin, Postprandial glucose, GI (Glycemic Index)
- CGM (Continuous Glucose Monitor)
A wearable device measuring glucose in interstitial fluid every few minutes, showing real-time readings and trend arrows. Examples: Dexcom G7, FreeStyle Libre 3.
See also: Time in Range (TIR), Blood glucose, SMBG (Self-Monitoring of Blood Glucose)
- Correction dose
An extra dose of rapid-acting insulin used to bring elevated blood sugar back to target, calculated as (current BG − target BG) ÷ correction factor.
See also: Correction factor (ISF), Rapid-acting insulin, Hyperglycemia
- Correction factor (ISF)
Insulin Sensitivity Factor — how many mg/dL (or mmol/L) one unit of rapid-acting insulin lowers blood sugar. Estimated using the 1800 Rule for rapid-acting insulin.
See also: Correction dose, TDD (Total Daily Dose), Insulin resistance
D
- Dawn phenomenon
A natural early-morning rise in blood sugar (roughly 2–8 AM) caused by cortisol, growth hormone, and glucagon release. Can cause elevated fasting glucose despite no overnight eating.
See also: Somogyi effect, Fasting blood sugar, Hyperglycemia
- Diabetes
A chronic metabolic condition characterized by persistently high blood glucose, resulting from insufficient insulin production, insulin resistance, or both.
See also: Type 1 diabetes, Type 2 diabetes, Prediabetes, Insulin
- DKA (Diabetic Ketoacidosis)
A life-threatening complication primarily of Type 1 diabetes in which insufficient insulin leads to high ketone production, causing metabolic acidosis. Symptoms: high blood sugar, ketones in urine/blood, nausea, abdominal pain, fruity breath.
See also: Ketones, Type 1 diabetes, Hyperglycemia
E
- eAG (Estimated Average Glucose)
A conversion of A1C into everyday blood sugar units (mg/dL or mmol/L) using the ADAG formula: eAG (mg/dL) = 28.7 × A1C − 46.7. More intuitive than A1C% for day-to-day context.
See also: A1C (HbA1c), Blood glucose
F
- Fasting blood sugar
Blood glucose after at least 8 hours without eating. Normal: 70–99 mg/dL; Prediabetes: 100–125 mg/dL; Diabetes: ≥126 mg/dL on two tests.
See also: Blood glucose, Prediabetes, OGTT (Oral Glucose Tolerance Test)
- Finger stick (finger prick)
A blood glucose test performed by pricking the fingertip with a lancet to obtain a blood drop for a glucose meter.
See also: Lancet, SMBG (Self-Monitoring of Blood Glucose), CGM (Continuous Glucose Monitor)
- Foot care
A critical routine for people with diabetes due to neuropathy and circulation issues. Includes daily inspection, proper footwear, and regular podiatrist visits.
See also: Neuropathy (diabetic), Diabetes
G
- Gestational diabetes
Diabetes that develops during pregnancy due to hormonal changes causing insulin resistance. Usually resolves after delivery but increases future Type 2 diabetes risk.
See also: Insulin resistance, Type 2 diabetes, OGTT (Oral Glucose Tolerance Test)
- GI (Glycemic Index)
A 0–100 scale ranking foods by how quickly they raise blood glucose compared to pure glucose. Low: ≤55; Medium: 56–69; High: ≥70.
See also: GL (Glycemic Load), Carbohydrate counting, Postprandial glucose
- GL (Glycemic Load)
A measure of blood sugar impact accounting for both GI and serving size: GL = (GI × grams of carbs) ÷ 100. Low: ≤10; Medium: 11–19; High: ≥20.
See also: GI (Glycemic Index), Carbohydrate counting
- Glucagon
A hormone produced by the alpha cells of the pancreas that raises blood sugar by signaling the liver to release stored glucose (glycogen). Used as an emergency treatment for severe hypoglycemia.
See also: Hypoglycemia, Glucose, Insulin
- Glucose
A simple sugar (monosaccharide) that is the body's primary fuel. Absorbed from food into the bloodstream after carbohydrate digestion.
See also: Blood glucose, Insulin, Carbohydrate counting
H
- Hyperglycemia
High blood sugar. Fasting above 130 mg/dL or post-meal above 180 mg/dL. Chronic hyperglycemia damages blood vessels and nerves, causing diabetes complications.
See also: Blood glucose, A1C (HbA1c), DKA (Diabetic Ketoacidosis), Neuropathy (diabetic)
- Hypoglycemia
Low blood sugar, typically below 70 mg/dL (3.9 mmol/L). Symptoms: shakiness, sweating, confusion, rapid heartbeat. Level 3 (severe): below 54 mg/dL (3.0 mmol/L), requires assistance.
See also: Rule of 15, Glucagon, Blood glucose
I
- IFCC
International Federation of Clinical Chemistry standard for reporting A1C in mmol/mol. Conversion: IFCC (mmol/mol) = (A1C% − 2.15) × 10.929.
See also: A1C (HbA1c)
- Insulin
A hormone produced by pancreatic beta cells that allows glucose to enter cells for energy. Essential for life; people with Type 1 diabetes must inject it externally.
See also: Basal insulin, Bolus insulin, Insulin pump, Insulin resistance
- Insulin pump
A wearable device delivering continuous basal insulin and mealtime bolus doses via a subcutaneous catheter, replacing multiple daily injections.
See also: Basal insulin, Bolus insulin, Type 1 diabetes
- Insulin resistance
A condition in which cells respond poorly to insulin, requiring higher levels to achieve the same effect. Central to Type 2 diabetes and prediabetes.
See also: Type 2 diabetes, Prediabetes, Metformin
- ISF (Insulin Sensitivity Factor)
See Correction factor.
See also: Correction factor (ISF)
K
- Ketones
Acids produced when the body burns fat for energy instead of glucose (due to insulin deficiency). High ketone levels indicate DKA risk. Measured via urine strips or blood ketone meters.
See also: DKA (Diabetic Ketoacidosis), Type 1 diabetes
L
- LADA (Latent Autoimmune Diabetes in Adults)
A slowly progressing autoimmune form of diabetes in adults, often initially misdiagnosed as Type 2. Confirmed by positive GAD antibody testing.
See also: Autoimmune diabetes, Type 1 diabetes, Type 2 diabetes
- Lancet
A small, sterile needle used with a lancing device to prick the fingertip for a blood glucose sample.
See also: Finger stick (finger prick), SMBG (Self-Monitoring of Blood Glucose)
- Long-acting insulin
See Basal insulin.
See also: Basal insulin
M
- Metformin
The most commonly prescribed first-line oral medication for Type 2 diabetes. Primarily reduces hepatic glucose production and improves insulin sensitivity. Does not cause hypoglycemia when used alone.
See also: Type 2 diabetes, Insulin resistance
- mg/dL
Milligrams per deciliter. The unit used in the United States for blood glucose. To convert to mmol/L, divide by 18.018.
See also: mmol/L, Blood glucose
- mmol/L
Millimoles per liter. The unit used in most countries outside the US for blood glucose. To convert to mg/dL, multiply by 18.018.
See also: mg/dL, Blood glucose
N
- Neuropathy (diabetic)
Nerve damage caused by prolonged hyperglycemia. Peripheral neuropathy (feet and legs) is most common; autonomic neuropathy can affect digestion, heart rate, and blood pressure.
See also: Hyperglycemia, Foot care, Diabetes
- NPH insulin
Neutral Protamine Hagedorn — an intermediate-acting insulin largely replaced by long-acting analogues. Still used in some settings.
See also: Basal insulin, Insulin
O
- OGTT (Oral Glucose Tolerance Test)
A diagnostic test in which blood sugar is measured 2 hours after drinking 75g of glucose. Prediabetes: 140–199 mg/dL; Diabetes: ≥200 mg/dL.
See also: Fasting blood sugar, Prediabetes, Gestational diabetes
- Ozempic (semaglutide)
A weekly injectable GLP-1 receptor agonist for Type 2 diabetes that lowers blood sugar and promotes significant weight loss.
See also: Type 2 diabetes, Insulin resistance
P
- Postprandial glucose
Blood sugar measured after eating, typically 1–2 hours after the start of a meal. Target for most people with diabetes: below 180 mg/dL.
See also: Blood glucose, Bolus insulin, GI (Glycemic Index)
- Prediabetes
Blood sugar above normal but below diabetic thresholds. Fasting 100–125 mg/dL, A1C 5.7–6.4%, or OGTT 140–199 mg/dL. Largely reversible with lifestyle changes.
See also: A1C (HbA1c), Fasting blood sugar, Insulin resistance, Type 2 diabetes
R
- Rapid-acting insulin
Insulin that starts working within 15 minutes, peaks in 1–2 hours. Used for mealtime coverage. Examples: lispro (Humalog), aspart (NovoLog), lispro-aabc (Lyumjev).
See also: Bolus insulin, Basal insulin, Correction dose
- Retinopathy (diabetic)
Damage to retinal blood vessels caused by chronic hyperglycemia. The leading cause of preventable blindness in working-age adults. Detected by annual dilated eye exams.
See also: Hyperglycemia, Diabetes
- Rule of 15
Standard hypoglycemia treatment: consume 15g of fast-acting carbohydrates, wait 15 minutes, recheck blood sugar. Repeat if still below 70 mg/dL.
See also: Hypoglycemia, Glucagon
S
- SGLT2 inhibitor
A class of oral diabetes medications (empagliflozin/Jardiance, dapagliflozin/Farxiga, canagliflozin/Invokana) that lower blood sugar by causing kidneys to excrete excess glucose in urine. Also cardio- and nephro-protective.
See also: Type 2 diabetes, Metformin
- SMBG (Self-Monitoring of Blood Glucose)
Regular testing of blood glucose by a person with diabetes using a finger-stick and glucometer.
See also: Finger stick (finger prick), CGM (Continuous Glucose Monitor), Blood glucose
- Somogyi effect
A morning blood sugar rebound caused by nighttime hypoglycemia triggering counter-regulatory hormones. Distinguished from the dawn phenomenon by checking blood sugar at 2–3 AM.
See also: Dawn phenomenon, Hypoglycemia, Blood glucose
T
- TDD (Total Daily Dose)
The total insulin dose taken in 24 hours, including basal and bolus. Used to calculate correction factor (1800 ÷ TDD) and carbohydrate ratio.
See also: Correction factor (ISF), Basal insulin, Bolus insulin
- Time in Range (TIR)
The percentage of time blood glucose stays within the target range (typically 70–180 mg/dL). A key CGM metric. ADA recommends >70% TIR for most adults with diabetes.
See also: CGM (Continuous Glucose Monitor), Blood glucose, Hyperglycemia, Hypoglycemia
- Type 1 diabetes
An autoimmune disease in which the immune system destroys beta cells, eliminating insulin production. Requires lifelong insulin therapy. Can develop at any age but commonly diagnosed in children and young adults.
See also: Autoimmune diabetes, Beta cells, Insulin, DKA (Diabetic Ketoacidosis)
- Type 2 diabetes
The most common form of diabetes, characterized by insulin resistance and relative insulin deficiency. Strongly associated with obesity and physical inactivity. Managed with lifestyle changes, oral medications, and/or insulin.
See also: Insulin resistance, Prediabetes, Metformin, SGLT2 inhibitor