Diabetics usually know of two Types of diabetes (imaginatively called Type 1 and Type 2). Not surprisingly, most diabetics in the world also fall under one of these two Types but there are others. In fact there are at least 6.5 Types (the half will be explained a bit further down) and not a complete consensus among the world’s diabetes associations. I will focus on the ones where debate in minimal.
For those who do not like to read, here is the list of Types. The rest of this blog will go into detail about each of them, how they are derived, diagnosed and treated.
- Type 1: About 10% of all diabetics
- LADA, aka Type 1.5: A subcategory of Type 1
- Type 2: Almost all of the other 90% of diabetics
- Type 3c: 0.5-1% of all diabetics (many others wrongly diagnosed as Type 1 or 2)
- MODY/NDM: 0.24% of those with diabetes
- Type 0: 1 in 2 million people
- Gestational: Approximately 13% of pregnant women (1 in 7)
What Makes a Type?
Diabetes Types are NOT classified by how the disease presents itself. This is important because it means the Type does not solely dictate how to treat the disease. Diabetes Types are ‘etiological’. This is a fancy word which means they are classified by the cause.
Type 1 diabetes is an auto-immune disease. This simply means the body’s immune system attacks the beta cells of the pancreas. How the immune system gets confused and attacks the body is not yet known. So, while the cause of Type 1 diabetes is known (the immune system) the cause of the cause (why the immune system is broken) is unknown.
Many websites out there characterize Type 1 as “not being able to produce insulin” but this is not the full story. As mentioned, diabetic Types are etiological so while most Type 1s produce little to no insulin (because the immune system is very good at its job), there are Type 1s, like me, who still produce enough insulin to live a relatively normal life.
In terms of diagnosis, when the patient first shows symptoms, a blood test for the auto-antibodies (the parts of the immune system which attach the pancreas) will confirm it is Type 1. If the person has been a diabetic for many years, as the beta cells of the pancreas are mostly destroyed, the immune response will be minimal, making a definitive diagnosis harder.
For treatment, while the patient is in ‘honeymoon’ (where their body can still produce some insulin) they may only need pills and a low carbohydrate/low GI diet to keep their blood sugars under control. However, eventually, the honeymoon will pass and they will need to inject insulin.
Type 2 is the most common Type of diabetes and the cause is unknown. This is the bucket all diabetics fall into when the cause cannot be discerned and as this is literally 9 out of 10 diabetics speaks strongly to the fact that we are only beginning to understand this disease and what causes it. Sadly, largely due to unawareness of the various Types in the medical community, there is much misdiagnosis when it comes to a person’s ‘Type’ with far too many being incorrectly dumped into the Type 2 category.
A ‘typical’ Type 2 cannot make enough insulin to meet their body’s needs. The pancreas is limited in its production and the cells of the body do not use the insulin efficiently (insulin resistance). Like Type 1s, the beta cells will show damage in Type 2 patients but the cause of the damage is unknown. One theory is the immune system temporarily attacks the pancreas but then stops, causing partial damage, but this has not yet been proven.
A common myth is that Type 2 diabetes is caused by ‘lifestyle factors’ i.e. eating unhealthy food, being overweight and not exercising. This is completely untrue. Type 2 is associated to things like obesity but it is not the cause. Where the association likely comes from is that a common cause of insulin resistance is fat deposits around the organs (visceral fat). So, if you are overweight, you may be contributing to your insulin resistance. However the underlying production limitation is still there. While reducing your carbohydrate intake and losing weight may get you off the medications, you are not cured, but simply in remission. Your impaired insulin production is still there; you are simply not testing the limit any more.
An analogy would be to suggest that asthma is caused by running because when some people run, they get an asthma attack. While asthma attacks are associated with exertion, the cause is completely separated; the exertion simply tests the limits imposed by the disease.
Unlike Type 1, there is a strong genetic component to Type 2 (although there is no genetic test for the disease). Type 2 runs in families and is significantly more prevalent in some areas of the world more than others.
Given the cause if unknown, diagnosis comes from exhausting the possibility of the other Types (or it should!) and giving the patient a glucose tolerance test to establish they have an abnormal response when processing sugars.
While insulin is sometimes needed, Type 2 is usually managed through pills, diet, and exercise. Progression of the disease is extremely slow and many Type 2s never require insulin to stay healthy.
LADA (Type 1.5)
LADA is also an auto-immune disease and, therefore, is a sub-category of Type 1. LADA stands for ‘Latent Autoimmune Diabetes of Adulthood’ and what makes LADA different to ‘typical’ Type 1 is the rate at which the disease progresses. This is what the word ‘latent’ means and why LADA is different to typical Type 1. While a typical Type 1 will be on insulin somewhere between immediately to a few weeks after diagnosis, LADA patients can survive without insulin for years.
Generally, LADAs are diagnosed later in life (for me it was at the age of 43) whereas ‘normal’ Type 1s are diagnosed much younger. Because LADA affects older people and the patient may not require insulin straight away, it is often misdiagnosed as Type 2. A simple blood test is all it takes to separate the LADAs from the Type 2s.
This was the test that the hospital failed to do in my case. As a male in his early 40s with a bit of extra padding, the ‘experts’ simply assumed I was Type 2. As LADA eventually leads to ‘classic’ Type 1 where the body no longer produces insulin, it differs to Type 2 which often never progresses to such a state. Therefore, the treatment of LADA is different to Type 2 because the focus is on preserving beta cells and prolonging the honeymoon, whereas in Type 2s it is assumed the remaining beta cell population will stay mostly constant for the rest of the patient’s life.
This misdiagnosis leads to many cases where someone who has been told they are Type 2, gets sicker and sicker as the medications become less effective. Often the misdiagnosis is eventually found but only after the patient has been ravaged with diabetic complications which may last the rest of the life e.g. eye damage, organ damage, nerve damage etc. All it takes is a simple blood test when the disease first presents itself to get the diagnosis right and to save the patient’s quality of life and a fortune in medical consultations and treatments.
The first of the lesser-known Types, Type 3c is NOT auto-immune but is where the pancreas is damaged by something else e.g. cancer, pancreatitis, cystic fibrosis, surgery etc. The damage may have also happened years before symptoms begin showing.
Given the cause is different we begin to see that this is important in how we approach the disease. Whereas the immune system selectively targets the beta cells (the cells of the pancreas which produce insulin) but usually ignores the alpha cells (which produce other hormones used for blood sugar regulation), damage caused by cancer or a car accident is less selective. Therefore, treatment which assumes the patient is Type 1 or 2 may miss the mark and, like the misdiagnosis of LADAs, may lead to diabetic damage before the error is revealed.
Diagnosis is through examining the patient’s history to see if there is a likelihood of damage and scanning of the pancreas to see the physical damage.
MODY (Maturity Onset Diabetes of the Young) and NDM (Neonatal Diabetes Mellitus) are monogenic forms of diabetes. Monogenic simply means caused by one broken gene. The name ‘Maturity Onset Diabetes of the Young’ is similar to terms like ‘Juvenile Diabetes’ and ‘Adult Onset Diabetes’ in that they come from a time when our technology was unable to definitively define the cause. Today, these terms are limited in their meaning but continue to hang around. I, for example, was diagnosed with ‘Juvenile Diabetes’ in my early 40s.
Most cases of MODY/NDM involve one of three specific genes but 11 gene mutations have been discovered so far. As MODY/NDM are genetic they strongly carry down family lines. While as a Type 1, your children have something like an additional 10% risk of having the disease, with MODY/NDM they have a 50% risk, 1 in 2.
The mutated gene means that a patient with MODY/NDM cannot produce insulin effectively and medication which seeks to stimulate the beta cells in some fashion may be useless in MODY/NDM patients. There is also a form of MODY (Glucokinase MODY) which affects blood glucose regulation but the principle that treatment due to misdiagnosis may be ineffective or counterproductive remains the same.
As MODY/NDM are strongly genetic, the patient’s broken beta cell machinery goes into operation at birth (arguably before birth but the mother can help compensate). For NDM, symptoms appear in the first 6-12 months of life (it is very rare for Type 1 to make an appearance this early), while for MODY symptoms usually appear in adolescence.
Definitive diagnosis comes from genetic testing, which is readily available. While misdiagnosis is, again, common, the correct diagnosis is vital as different forms of MODY/NDM respond to different drugs or, in the case of Glucokinase MODY, no treatment may be needed at all (Glucokinase MODY has the patient run a slightly high blood glucose but often not dangerously so). The other reason correct diagnosis is important is because of the risk to a patient’s children of having the same disease. Knowing this means it can be tested for and treated before complications arise.
Type 0 Diabetes
This disease is also called Glycogen Storage Disease Type 0. While also caused by genetic mutations, rather than affecting the machinery that produces insulin, it affects the machinery which uses the insulin to move blood sugar into cells for storage.
One of the things insulin does is move glucose out of the blood and into cells. Excess glucose is usually converted to ‘glycogen’ and stored in the cells (mainly in the liver but also in muscles) as an emergency energy source in times of exertion. In patients with Type 0, they cannot produce glycogen and therefore they have no energy backup.
The upshot of this is a patient with Type 0 can faint doing something as simple as climbing a set of stairs. Because there is no backup energy source and because it is hard to shift excess glucose out of the blood, a Type 0 patient will have wildly fluctuating blood glucose levels and the usual diabetic treatments (insulin and glucagon injections) are completely ineffective. If you think you have it tough as a Type 1, consider the plight of the Type 0.
As the disease presents in a very different way to the other Types e.g. fainting when climbing stairs, misdiagnosis is less common. Treatment is difficult and the best protocols are still being determined.
As the name suggests, gestational diabetes occurs during pregnancy so this one is exclusively female. The mechanism is broadly understood; to grow a baby, glucose needs to reach the fetus. To make this happen, the woman’s body releases hormones which increase insulin resistance in her own body, limiting access to glucose and allowing it to get to the baby.
With increased insulin resistance, the pancreas needs to release more insulin to keep up with the woman’s energy demands (up to three times as much in fact) which can test the pancreas’ limits and lead to diabetes. Excess glucose in the blood can make the baby grow excessively, leading to birthing complications but can also damage the baby leading to miscarriage or stillbirth so it is important that Gestational Diabetes is managed during pregnancy and, thankfully, screening for it is common.
Once the baby is born and the pregnancy hormones disappear, the diabetes usually goes as well. However, in some cases, the damage is done and the diabetes remains, generally classified as Type 2 and treated as such. Arguably, the cause is known so it is not really Type 2 and is a continuation of Gestational Diabetes.
What is Your Type?
If you are a Type 2 and your treatment plan is not working well, it is worth considering that you may have been misdiagnosed. If, after reading the above, you feel you may be a candidate for a different Type, reach out to a medical professional to discuss your concerns. While medical professionals hate Dr Google and well meaning blogs, it is your life and you who will have to live with the complications if their guess was wrong. They can organize the tests to make a definitive diagnosis.
Thanks for posting this.
There is another Type, it doesn’t have a name as such as there is so little patients that survived birth.
But I have a daughter that did, there is around 10 in the world that are living with it.
It’s Called Pancreatic Agenesis, causes my a deletion of a gene called GATA6. The patients are born without a Pancreas, Gall bladder and have either malformations of the Heart or the Bilary System. All have been born premature with extremely small birth weights (my daughter was born at 31 weeks and 735 grams)
The first sign is extremely high blood sugar within hours of birth, in our case my daughter had a Blood Glucose of 56mmol at 6 hours old
Thank you so much for writing this!
When I originally promoted this article I was shouted down for suggesting Type classification was etiological, especially on Reddit. To support my case, here is a text book on the subject confirming this classification approach. https://www.google.com.au/books/edition/Principles_of_Diabetes_Mellitus/FEPjBwAAQBAJ?hl=en&gbpv=1&dq=diabetes+type+etiology&printsec=frontcover