Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea; they are not medical tools.
Tap the buttons and slide the sliders.
Tap the lunch to send glucose into the blood. Then switch insulin off. What happens to the cells?
Add a meal, then switch insulin off: blood glucose climbs while the cells' fuel runs down.
Tap the lunch. Then turn the keys off. Are the cells still fed?
Drag the insulin keys onto the doors. Watch the glucose flow in and the blood sugar fall.
Drag insulin to the cells by hand, or let the beta cells respond to the glucose level automatically.
Drag a blue key onto a door. In goes the sugar!
Slide how many beta cells are left. Then give insulin, the way people with type 1 do every day.
As beta cells are lost, insulin output falls and glucose accumulates. An insulin dose replaces the missing keys.
Slide the key makers away. Then give insulin. Does the sugar go in again?
Stiffen the locks. The pancreas works harder and harder. Then go for a walk.
Raise resistance: the beta cells compensate with extra insulin. Activity improves insulin sensitivity.
Make the locks stiff. Then go for a walk. Do the locks work better?
Pick a body, then add insulin or a walk. Where is the curve after 2 hours?
Compare normal, insulin-deficient and insulin-resistant responses. In the glucose drink test, 200 mg/dL or more at 2 hours points to diabetes.
The curves are simplified illustrations, not real patient data.
Tap each spot to see how years of high blood sugar can affect that part of the body.
Chronic hyperglycaemia damages small vessels and nerves: eyes, kidneys, feet, heart.
Tap a spot on the body.
This explains how the body works; it isn't medical advice. If you're worried, talk to a doctor.
If you feel worried or unwell, tell a grown-up. A doctor can help.
Diabetes is when there is too much sugar in the blood. Here is how it happens.
When you eat, your body turns most of the food into a sugar called glucose. Your blood carries it to tiny cells all over your body. Sugar is their food.
Many cells, like muscle cells, are like a little room with a locked door. Your body makes keys called insulin. A key opens the door, and in goes the sugar.
In type 1, the body's germ fighters break the key makers by mistake. Nobody gets it from eating sweets, and it is nobody's fault. Kids with type 1 get insulin every day, and they can run and play like everyone else.
In type 2, there are keys, but the locks are stiff. Grown-ups get it more often. Many things mix together to cause it. Moving and playing help the locks work better.
This page explains how the body works; it isn't medical advice. If you're worried about your health or someone else's, talk to a doctor.
Diabetes is when the amount of sugar (glucose) in your blood stays too high.1 It happens because the body makes too little insulin, or can't use insulin well, or both.15 Insulin is a hormone made by the pancreas, and it works like a key that lets glucose into your cells.5 Without enough working keys, glucose stays stuck in the blood, and the cells go short of fuel.2
Your body breaks most of the food you eat down into glucose and releases it into your bloodstream.5 Glucose is your body's main source of energy.1 But glucose can't simply walk into a cell. When blood sugar rises after a meal, it signals the pancreas, an organ in your belly, to release insulin.8
Inside the pancreas are about a million tiny clusters of cells called islets. Around three-quarters of the cells in each islet are beta cells, and they are the ones that make insulin.13 Insulin travels in the blood and "acts like a key to let blood sugar into your body's cells for use as energy," as the CDC puts it.5 Muscle, fat and liver cells are the main places it opens up.213 Insulin also tells the liver to store extra glucose for later; between meals the liver releases it again, so energy is always available.8
When the system works, blood sugar rises after a meal and then falls back to normal. In diabetes, the key system breaks down in one of two main ways. Similar keys and locks run all over your body: enzymes, for example, fit their molecules like keys too (see how enzymes work).
Type 1 diabetes is an autoimmune condition: the immune system, which normally fights infections, attacks the body by mistake.36 It destroys the beta cells in the pancreas, so the body makes little or no insulin.3 This attack can go on for months or years before any symptoms appear.6
Why does the immune system do this? Scientists are still finding out. Some people have genes that raise their chances, but many people with those genes never get type 1. A trigger in the environment, such as a virus, may also play a part.6 What is clear is this: "Diet and lifestyle habits don't cause type 1 diabetes."6 Nobody gets it from eating sweets, and it is nobody's fault. No one yet knows how to prevent it.5
Type 1 often starts in children, teens and young adults, but it can begin at any age.6 People with type 1 need to take insulin every day, by injection or with an insulin pump.312 It takes extra work, but with the right support, people with type 1 lead full and healthy lives.12 About 5 to 10% of people with diabetes have type 1.5
In type 2 diabetes the pancreas still makes insulin, but cells in the muscles, fat and liver don't respond to it normally. This is called insulin resistance.27 The pancreas makes more insulin to try to get the cells to respond. Over time it can't keep up, and blood sugar rises, first to prediabetes and then to type 2 diabetes.478
Researchers don't fully know what starts this process, but some things make it more likely:27
You can't tell if someone has insulin resistance by looking at them, and you don't have to be overweight to have it.8 Some risk factors, like age and family history, can't be changed. Others can: being active, eating healthily, keeping a healthy weight and not smoking can prevent or delay type 2.25 Physical activity helps directly, because it makes your cells more sensitive to insulin.8 Type 2 is by far the most common kind: about 90 to 95% of cases.5
| Type 1 | Type 2 | |
|---|---|---|
| The problem | Too few keys: little or no insulin3 | Stiff locks: cells resist insulin, and the pancreas can't keep up7 |
| Cause | Immune system destroys beta cells by mistake6 | Not fully known; genes, age, weight and inactivity raise the risk2 |
| Caused by diet? | No6 | No single food; overall habits affect the risk2 |
| Usually starts | Childhood, teens, young adults (any age possible)6 | Adults, but more and more young people5 |
| How it develops | Symptoms can appear in weeks or months6 | Over years, often with no noticeable symptoms7 |
| Share of cases | About 5–10%5 | About 90–95%5 |
| Managed with | Insulin every day3 | Healthy eating and activity, plus medicines or insulin if needed7 |
Gestational diabetes can develop during pregnancy, when the body can't make the extra insulin it needs. Pregnancy hormones are thought to play a role.2 It is usually checked for between weeks 24 and 28 of pregnancy.9 It usually goes away after the baby is born, but it raises the chance of type 2 diabetes later in life.5
Doctors find diabetes with blood tests.9 In a glucose tolerance test, you drink a sugary liquid and your blood sugar is measured afterwards. In our sugar-meter toy you can watch the idea: in a body that works, blood sugar rises after a meal and comes back down.
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| 2 hours after a glucose drink | below 140 mg/dL | 140–199 | 200 or above |
| Fasting blood sugar | 99 or below | 100–125 | 126 or above |
| A1C (average over 2–3 months) | below 5.7% | 5.7–6.4% | 6.5% or above |
Source: CDC.9 The curves in the explainer are simplified illustrations, not real patient data.
Common signs of high blood sugar include peeing a lot, feeling very thirsty or hungry, blurry vision, tiredness and sores that heal slowly.2 Type 2 often has no noticeable symptoms at all, and more than 1 in 4 adults with diabetes don't know they have it.57
Over many years, blood sugar that stays high can damage the heart, kidneys, nerves, feet and eyes.13 In the United States, diabetes is the leading cause of kidney failure, lower-limb amputations and adult blindness.5 Nerve damage can take away feeling in the feet, so small cuts may go unnoticed; that's why feet get checked at health visits.2 The good news: keeping blood sugar close to target helps prevent or delay these problems.37
The retina is the light-sensing layer at the back of your eye. High blood sugar changes the tiny blood vessels that feed it: they can weaken, bulge, leak fluid or bleed. This is called diabetic retinopathy.1011 Leaking fluid can make the centre of the retina swell and blur vision. Diabetic retinopathy is the leading cause of blindness in working-age adults.11 Early stages usually have no symptoms, so people with diabetes should have a dilated eye exam at least once a year; found early, treatment can stop the damage.10
Insulin was discovered in 1921 by Canadian scientists Frederick Banting and Charles Best, and Banting shared the Nobel Prize for it in 1923.13 Today insulin, other medicines, healthy food and activity help people manage every type of diabetes.57
Diabetes happens when blood sugar stays too high because the body makes too little insulin or can't use it well. In type 1, the immune system destroys the insulin-making beta cells by mistake. In type 2, cells resist insulin and the pancreas can't keep up; genes, age, extra weight and inactivity raise the risk. Gestational diabetes appears during pregnancy.
Not directly. Type 1 diabetes is caused by an immune reaction, and diet and lifestyle habits don't cause it. Type 2 has many risk factors, including family history, age, body weight and physical activity. No single food causes it, though an overall healthy way of eating and staying active lower the risk.
Type 1 develops when genes and possibly an environmental trigger, such as a virus, lead the immune system to attack the beta cells; it often starts in childhood but can begin at any age. Type 2 develops slowly over years as insulin resistance builds and the pancreas can't keep up.
In type 1 the body makes little or no insulin (too few keys), so people need insulin every day. In type 2 the body still makes insulin but the cells don't respond well to it (stiff locks). Type 2 is far more common, making up about 90 to 95% of cases.
Blood sugar that stays high for years damages small blood vessels and nerves. In the eyes, the tiny vessels of the retina can weaken, leak or bleed (diabetic retinopathy). It can also harm the kidneys, nerves in the feet and the heart. Keeping blood sugar in range and having a yearly eye exam help protect against this.
No one knows how to prevent type 1 yet. Type 2 can often be prevented or delayed with regular physical activity, healthy eating, reaching a healthy weight and not smoking, especially for people with prediabetes.
Genes play a part in both main types. Having a parent, brother or sister with diabetes raises your chances, but many people with risk genes never develop it. For type 1, something in the environment, such as a virus, may also play a part; for type 2, extra body weight, moving less and age also matter.