"Diabetes" is not one disease. It is a name for a pattern, too much glucose in the blood, that can arise in several different ways. Knowing which way matters, because it changes what treatment makes sense, what to expect, and even what family members should watch for. It also matters for a second reason. Because so many people share a single word for very different conditions, an enormous number of myths have grown up around it, and they travel easily from kitchen to kitchen and country to country.

This chapter has two jobs. First, it sorts diabetes into its main types and explains, using the language of Chapter 1, what goes wrong in each. Second, it takes the myths that cause the most harm and checks them against the evidence, one at a time.

3.1 Type 1 Diabetes: When the Immune System Turns Inward

A supply problem, not a signalling problem

In Chapter 1, insulin was the doorbell: a signal that tells muscle and fat cells to open their glucose doors. In type 2 diabetes, the main problem is that the doorbell is answered poorly. In type 1 diabetes, the problem is different: the doorbell is barely being rung at all. The immune system mistakenly attacks and destroys the insulin-producing beta cells of the pancreas, so little or no insulin is made.[@idf2021] People with type 1 diabetes need insulin every day to stay alive.[@idf2021]

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Type 1 diabetes is not caused by eating sugar, by being overweight, or by anything a parent did or did not do. It is an autoimmune condition. It is most often diagnosed in children and young adults and is one of the most common chronic diseases of childhood,[@idf2021] but, as we will see below, it is far from limited to them.

It starts long before the symptoms

One of the most important advances in this field is the understanding that type 1 diabetes has stages, and that the first stages happen silently. An expert group of JDRF, the Endocrine Society, and the American Diabetes Association proposed three:[@insel2015]

• Stage 1: The immune attack has begun and can be detected in the blood as two or more islet autoantibodies, but glucose is still normal, and there are no symptoms.
• Stage 2: The autoimmune attack continues and glucose has begun to run abnormally high (dysglycaemia), but there are still no symptoms.
• Stage 3: Symptoms appear and diabetes can be diagnosed: increased thirst, frequent urination, unexplained weight loss, and tiredness.

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This matters because, for the first time, there is something to do at stage 2. In a trial of 76 people, most of them children, who were relatives of someone with type 1 diabetes and who had two or more autoantibodies plus abnormal glucose, a course of an antibody treatment called teplizumab delayed the diagnosis by a median of roughly two years compared with placebo.[@herold2019] In November 2022 the US Food and Drug Administration approved it to delay the onset of stage 3 in people aged 8 years and older with stage 2 type 1 diabetes.[@sanofi2022] The wording is important: it delays, it does not prevent or cure, and it is used under specialist care. Approvals and age limits for this class of treatment have been changing, so if this is relevant to you or a relative, ask a paediatric or adult endocrinologist for current advice. Screening for the early stages is mainly available through research programmes and specialist clinics, and access varies enormously from country to country.

"Childhood diabetes" that begins in adulthood

One of the most persistent myths, which we will return to in section 3.3, is that type 1 diabetes only affects children. It does not. In a US national survey of about 950 adults with type 1 diabetes who use insulin, 37 percent reported that they had been diagnosed at age 30 or later.[@fang2023] The figure is self-reported and comes from one country, but it makes an important point: an adult who develops diabetes is not necessarily an adult with type 2.

There is also a slower-moving autoimmune form that appears in adults, called latent autoimmune diabetes in adults (LADA). Depending on the study and the population, it accounts for something in the range of 2 to 12 percent of adult-onset diabetes.[@buzzetti2020] People with LADA can look like they have type 2 diabetes at first, and may respond to tablets for a while, but their beta cells are being lost more quickly than in ordinary type 2. An international expert panel has proposed matching treatment to how much insulin the person's body still makes, measured by a blood test called C-peptide.[@buzzetti2020] If you were diagnosed as an adult but are lean, are losing weight without trying, or are not responding to treatment as expected, it is reasonable to ask your doctor whether antibody or C-peptide testing has been done.

Science Corner: Why autoantibodies? Autoantibodies are proteins made by the immune system that mistakenly target the body's own tissues. In type 1 diabetes, they are directed at proteins in the beta cells. They do not themselves destroy the cells, but their presence, especially two or more different ones, is a marker that the immune attack is under way. That is the basis of the staging system: the stages are defined by autoantibodies and glucose, not by symptoms.[@insel2015]

3.2 Type 2, Gestational, and the Rarer Types

Type 2: the common one

Type 2 diabetes accounts for over 90 percent of all diabetes worldwide.[@idf2021] It is closely linked to overweight and obesity, increasing age, ethnicity, and family history.[@idf2021] It is the condition we have been following through Chapters 1 and 2: insulin resistance develops, the pancreas compensates for years, and eventually beta cells can no longer keep up. Its symptoms are usually much less dramatic than those of type 1, and it may be completely symptomless.[@idf2021]

Type 2 is also a progressive condition in most people: beta-cell function tends to decline over time.[@weir2004] That is not a personal failure. It is why treatment often needs to be adjusted over the years, and why we look at medicines, including insulin, in Chapter 11.

Gestational diabetes

Gestational diabetes mellitus (GDM) is raised glucose first recognised during pregnancy. Hormones made by the placenta make the mother's cells more resistant to insulin, and in some women the pancreas cannot compensate. According to the International Diabetes Federation's 2025 estimates, around 1 in 5 live births is affected by hyperglycaemia in pregnancy,[@idf2025fact] and most (75 to 90 percent) of those cases are gestational diabetes.[@idf2021] Testing during pregnancy, usually in the second half, is how it is found.[@ada2026]

GDM usually settles after delivery, but it is a warning for the mother's future. A large meta-analysis of 20 studies covering more than 675,000 women found that women who had gestational diabetes had a 7.43 times higher risk of later developing type 2 diabetes than women whose pregnancies had normal glucose.[@bellamy2009] The IDF notes that the risk is particularly high in the three to six years after the pregnancy.[@idf2021] If you have had gestational diabetes, at any time in the past, that is worth telling your doctor and worth a periodic glucose test. It is also a reminder that prediabetes (Chapter 2) can be caught and turned around.

The rarer types

The remaining group is small in numbers but important, because it is often misdiagnosed.

• Monogenic diabetes (including the forms known as MODY, maturity-onset diabetes of the young) is caused by a change in a single gene rather than by the mix of many small influences behind type 2. It is estimated to represent 1.5 to 2 percent of all cases, and probably more, because it is often misdiagnosed as type 1 or type 2.[@idf2021] Clues that suggest it include diabetes in several generations of a family, diagnosis at a young age, and no typical features of type 1 or type 2. A genetic test can confirm it, and for some forms the diagnosis changes treatment.
• Diabetes caused by other conditions or medicines, for example diseases of the pancreas, some hormonal conditions, and certain drugs, is also recognised in the classification used by the American Diabetes Association.[@ada2026]

Side by side

Sources: IDF Diabetes Atlas.[@idf2021] Pregnancy treatment and monogenic-diabetes treatment vary and should be decided with a specialist.

Science Corner: Why the type matters for the numbers Because both type 1 and type 2 raise glucose, the tests we meet in Chapter 4 cannot tell them apart. What can help are the person's story (age, speed of onset, weight change, family history), and sometimes special tests: autoantibodies for autoimmune diabetes, and C-peptide, which shows how much insulin the body is still making. None of these is needed in every case, but they are worth asking about when the picture does not fit.[@buzzetti2020]

3.3 Global Myths, Checked

Myths about diabetes are stubborn because each contains a grain of truth. The list below is not exhaustive. It covers the beliefs that, in my judgement, do the most harm, by delaying a test, encouraging shame, or leading people to stop a treatment that works. You will probably recognise a version of some of them from your own family, whatever kitchen you grew up in.

Myth 1: "Sugar causes diabetes."

The evidence: partly true, but far too simple. Type 1 diabetes is autoimmune and is not caused by eating sugar.[@idf2021] Type 2 diabetes arises from insulin resistance, which is linked to body fat, age, ethnicity, and family history.[@idf2021] Sugary drinks do, however, appear to add risk. A meta-analysis of 8 prospective studies with over 310,000 participants found that people who drank one to two servings of sugar-sweetened drinks a day had a 26 percent higher risk of type 2 diabetes than those who rarely drank them.[@malik2010] That is an association from observational studies, not proof of cause, but it is consistent enough that the American Diabetes Association's consensus report advises replacing sugar-sweetened beverages with water as often as possible.[@evert2019] The takeaway is not "sugar alone is the villain". It is that liquid sugar is an easy place to make a difference.

Myth 2: "Only overweight people get type 2 diabetes."

The evidence: overweight is a strong risk factor,[@idf2021] but not the only one. As Chapter 1 explained, what matters is where fat is stored, and normal-weight people can carry harmful fat in the liver and around the organs.[@thomas2012] In people of Asian descent, metabolic risk appears at lower body weights, which is why the WHO described BMI values of 23 and above as an increased-risk range for this group.[@who2004bmi] Do not use your weight alone to decide whether you need a test.

Myth 3: "Type 1 diabetes is a childhood disease."

The evidence: false. As we saw in section 3.1, 37 percent of US adults with type 1 diabetes in one survey were diagnosed at 30 or older,[@fang2023] and LADA accounts for a meaningful share of adult-onset diabetes.[@buzzetti2020] Adults with type 1 are sometimes wrongly told they have type 2, which can delay the right treatment.

Myth 4: "Needing insulin means you failed, and insulin causes the complications."

The evidence: false on both counts, and it is one of the most costly myths. In one study of adults with type 2 diabetes who were not yet taking insulin, more than a quarter said they would not be willing to start it if their doctor recommended it.[@polonsky2005] Yet type 2 diabetes tends to progress as beta-cell function declines,[@weir2004] so needing insulin is often simply where the biology has led, not a moral verdict. And the complications people fear come from long-term high glucose, not from the medicine that lowers it. In the landmark Diabetes Control and Complications Trial, people with type 1 diabetes who used intensive insulin treatment to bring glucose closer to normal developed fewer long-term complications and progressed more slowly than those on conventional treatment.[@dcct1993] Insulin is a tool, and in the right hands it protects your eyes, kidneys, and nerves.

Myth 5: "A herbal remedy or a special food can cure diabetes."

The evidence: no herb, spice, or single food has been shown to cure diabetes. Take bitter melon, widely used across Asia, Africa, and Latin America. A Cochrane review of four randomised trials with 479 participants found insufficient evidence on its effects in type 2 diabetes, and noted that the preparations differed too much in quality to make recommendations.[@ooi2012] That does not mean traditional foods and remedies are worthless. It means they should never replace tested treatment, and you should tell your care team about anything you take, so that it can be considered alongside your medicines.

Myth 6: "Reversing type 2 diabetes means you are cured."

The evidence: not quite, and the word matters. An international consensus report defines remission as an HbA1c below 6.5 percent measured at least three months after stopping all glucose-lowering medication, and advises checking again at least once a year.[@riddle2021] Remission is achievable for some people. In the DiRECT trial in Scotland and England, 306 adults diagnosed with type 2 diabetes in the previous six years were assigned to a supervised programme of total diet replacement of about 825 to 853 kcal a day for 3 to 5 months, then gradual food reintroduction, with support. After 12 months, 46 percent were in remission, compared with 4 percent of the group receiving usual care.[@lean2018] Three cautions apply. The programme was supervised. It included people with fairly recent diagnoses who were not taking insulin. And remission is a state you keep by continuing the habits and follow-up, not a permanent discharge. It also does not apply to type 1 diabetes. If you are on medication, please do not stop it on your own; changes should be made with your care team.

Myth 7: "With diabetes, you can never eat carbohydrates, fruit, or sweets again."

The evidence: false. The American Diabetes Association's consensus report on nutrition concluded that there is no ideal percentage of calories from carbohydrate, protein, and fat that suits everyone, and that many eating patterns can work if they are individualised.[@evert2019] What the healthful patterns have in common is minimising added sugars and refined grains.[@evert2019] Part 2 of this book is devoted to eating well across many cuisines, without giving up the foods that carry your culture and family life.

Myth 8: "It's your fault," or "It's a punishment."

The evidence: there is no single cause, and no moral one. Type 1 is autoimmune. Type 2 is shaped by genetics, ancestry, age, and the environment we live in, alongside behaviour.[@idf2021] Shame is not a treatment. In fact it can make people put off getting tested and treated: one of the voices at the start of this book admits to having "buried my head in the sand". If a friend or family member has said something like this to you, you now have a way to answer it.

Key Takeaways

• "Diabetes" is a family of conditions. The main ones are type 1 (autoimmune, little or no insulin), type 2 (insulin resistance followed by beta-cell decline, over 90 percent of cases), gestational, and rarer types such as monogenic diabetes.
• Type 1 diabetes has silent early stages that can be detected with autoantibodies. A treatment that delays stage 3 onset exists for people with stage 2, but it delays rather than prevents.
• Type 1 can start at any age. In one US survey, 37 percent of adults with type 1 were diagnosed at age 30 or later, and slower autoimmune forms (LADA) can be mistaken for type 2.
• Gestational diabetes usually resolves after delivery, but women who have had it carry a much higher long-term risk of type 2, so follow-up tests matter.
• Myths cost people time and dignity. Sugar alone does not cause diabetes, but sweet drinks add risk. Herbal remedies have not been shown to cure it. Insulin is not failure, and remission is not a cure.
• Any single label is a starting point. If your diagnosis or your response to treatment does not fit the usual picture, ask your doctor about the type.

Action Points

1. Know your type. If you or a family member has diabetes, find out which type it is, and when and how it was diagnosed. If it does not seem to fit the usual picture, ask whether antibody or C-peptide testing or genetic testing would be useful.
2. If you had gestational diabetes, book a glucose test if you have not had one in the past year or two, and tell any new doctor about it.
3. Check your family tree for patterns. Diabetes in several generations, especially with diagnosis at a young age, is worth mentioning to a doctor.
4. Do a myth audit. Write down three things you have heard about diabetes from family, friends, or social media. Check each against this chapter, and if you are unsure, bring it to your care team.
5. Swap one sweet drink a day for water for two weeks. It is a small change, and it is the one on which the evidence in this chapter is most consistent.

This book is intended for education and does not replace personal medical advice. If you have diabetes or take glucose-lowering medication, please consult your healthcare team before changing your diet, exercise, or treatment.