Misdiagnosis of Adult-Onset Type 1 Diabetes: Root Cause Analysis

I do advocacy to bring awareness to the prevalence of adult-onset Type 1 diabetes/LADA and the problem of misdiagnosis–I was misdiagnosed 25 years ago. I just did a misdiagnosis root cause analysis–here are my top three reasons for misdiagnosis:

· Persistent myth that Type 1 diabetes is a childhood disease and that adults can’t get it

· Lack of knowledge of the heterogenous phenotype of adult-onset Type 1 diabetes

· Doctors’ lack of time

And here is a link to my blog, where I go into much more depth. I welcome your thoughts, comments, and input!


I have been a type 1 since 2003.

Two other mentions for me. The not skinny I have run across with other people too.

One is fitting more of the profile of type 2. I was misdiagnosed for over 8 years and I honestly believe it’s because I was never a skinny person. not obese, but not skinny and my GP and endo at the time just assumed I was a type 2. I even asked if I could be a type 1 as I had an uncle that was a type 1. They never even tested me, just kept trying new drugs. It wasn’t until I switched doctors that she sent me to a new endo who tested me without me even knowing and I was diagnosed right. I swam 75 laps 5 days a week and had been a vegetarian since I was 11, then a vegan, and type 2 never made sense to me and the drugs just made me sick. I refused to take anymore drugs after a few years and luckily asked for insulin.

The second thing is lack of knowledge of doctors (and people) and I guess that sort of fits that persistent myth of childhood onset too. When I asked my doctor for the second or third time, if I could be a type 1? Her answer, no the drugs wouldn’t work at all if you were a type 1. This from a GP doctor.

I did have a chiro just 4 years ago say to me I could be cured because I didn’t get it as a kid.

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Thanks, @Marie20, excellent comments. I do mention in my blog that another myth that gets in the way of a correct diagnosis is the assumption that someone who is overweight (or “no longer at fighting weight” as I like to say) can’t get Type 1. Sounds like you weren’t overweight, but just not skinny. And good point about the Type 2 drugs–yes, they work on almost ALL new onset Type 1s–back in the 1970s in the US, some children were put on sulfonylureas when first diagnosed, so they wouldn’t have to go on insulin immediately. And the sulfonylureas worked for a time. But doctors have these misconceptions…

Let’s not forget that there are dozens of flavors of diabetes, not just type 1 and or type 2, LADA, MODY etc. I have been treated at Joslin Boston for more than 30 years and they still have not been able to type me. My extensive test results (A1C, glucose tolerance, C-Peptide, GAD, MODY etc.) and profile does not fit any of their other patients. We just know that fast acting insulin + Dexcom CGM, alone, keeps me with an A1C below 6 so my endo and I no longer try to match me to a type. I am on MDI and dose every 2-4 hours during the day in 0.1 iu units, not on a pump.


I fit nearly every stereo type for type 1 and was still misdiagnosed for the first visit anyway. I was hospitalized and diagnosed correctly

I was 21,6’3 and 155 lbs. very fast onset. I was in DKA fasting sugar of 650.
The doc told me to restrict carbs and come back in 2 weeks.
I got myself to the hospital the next day.

Presently the tests to properly diagnose diabetics are very easy and routine. I dont know why this issue persists.


I seriously believe I have been misdiagnosed more times by doctors than I have been correctly diagnosed. One time I had a very bad stomach ache and went to the ER and they told me it was my appendix and wanted to take it out that day. I knew enough to know that an appendicitis was on the right side and not where I was having pain so I refused. They tried to scare me and told me my life was in danger but I still refused. Next day I was fine. I could tell half a dozen stories like this. I have very little faith in a doctors opinion at this point.

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Thanks for sharing. I also have LADA and had quite the run around before a correct diagnosis. I’m 30 and was diagnosed as Type 2 originally six years ago and I definitely did not fit the bill. Luckily was well controlled on Lantus after complete failure on orals so no one questioned it further (should have questioned it from the start) til the sugars started creeping back up . Even then the next move was always to try novel and overly expensive orals instead of actually trying find the root cause . It was frustrating.

It wasn’t until I did my own research on LADA and asked to be tested for GAD, IAA, ISA markers in conjunction with c-peptide that I got real answers . It was the magic bullet, all the answers I needed after a 5 minute blood draw and now have my sanity back on MDI.

It really pays off to know your body and arm yourself with as much knowledge as humanly possible . Doctors have the purest intentions but are highly overwhelmed and overburdened and struggle thinking outside the box at times. The disease has many masks.


Well done, @Melitta! Your reasoned, calm, and logical article, complete with citations should be published in a medical journal.

Thus, there is no obligation to diagnose, classify, and appropriately treat the different diseases that fall under the term “diabetes.” If there were a standard or guideline, doctors would be held accountable to the minimum standard of care: anything less would be malpractice.

I think the solution lies in adopting a standard of care that requires use of autoantibody tests before a diagnosis is given. This would solve this problem.

With your writing about this issue over the years, I understand that I was so lucky that a young general practitioner diagnosed me correctly at the age of 30 back in 1984. He didn’t perform any antibody or c-peptide tests. Looking back, he seems to have gone with a gut instinct and I consider myself lucky that he was right!

These days, with autoantibody tests available and inexpensive, there is no excuse for misdiagnosis. The medical profession needs to up their game. Thank-you for your continuing devotion to this important issue!


Thanks, Terry. I wish I could get published, as it seems I am the only one writing about the problem of misdiagnosis! It remains an enormous problem–these days the misdiagnosed show up on several Facebook pages I belong to–there is a steady stream of people who have been misdiagnosed.

It is interesting that the ADA Standards of Care 2020 has now acknowledged that “misdiagnosis is common.” Dr. Hirsch, who I interviewed for an earlier blog on the problem of misdiagnosis, is one of the contributors to the Standards of Care–maybe he instigated the new language?

Yes, you were lucky to get correctly diagnosed. Doctors who are good at the art of the interview and who actually look at their patients really do have a good chance of diagnosing correctly even without autoantibody testing.

Next blogs will be on potential solutions to the problem and also a field guide to identifying a person with adult-onset Type 1 diabetes. I did a field guide a while back, but I need to update it with info on slowly progressive Type 1.

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That seems likely and it helps that he lives with T1D as well. I know professionals tend to shy away from personal testimonials but I do think that skin in the game focuses attention in a way that other factors do not.

That’s the problem. It does persist. A lot. And like @Melitta stated, it’s happening in other countries too. UK even has a higher percentage of type 1’s per their population and people are still constantly misdiagnosed there.

I realize doctors are limited on time. But you would think since it’s such a problem that some kind of education on their annual follow up schooling would be required. But it almost seems like the world hasn’t really paid attention to the fact that 50% of the people get it after they are 30.

And while some countries don’t have a lot of their population getting type 1, that’s a little more understandable if it’s a rare, there is a decent amount of people with type 1 in the US and the UK and it’s costly when they are seriously sick. You would think they would work to make sure doctors pay attention to it.

Because of more knowledge now, because of having type 1. I am flabbergasted that I asked my GP and endo if I could be a type 1 and stated because of my uncle having type 1 and they never bothered to test me and just kept trying oral drugs that made me sick and watched my blood sugars climb. And by the second and third time I asked, I believed them and gave up asking. Thank goodness I eventually switched doctors.

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I was diagnosed as type 2 at age 67 by my PCP with an a1c of 8.1. I tried diet and exercise. My a1c went down and then back up. I started metformin, same result. Added gliburide, same result. By then I also had lost 30 pounds. I went to a type 2 class at a local endo clinic. During a break they gave us each a meter. My reading was 428. I think they were surprised I was walking. I made an appointment with a CDE and she ordered the antibody tests and c-peptide test. Came back type 1. My PCP said the tests were a waste of money because he was going to put me on insulin anyway!


Obviously your PCP is also unaware of the requirement that Medicare and some other insurance plans need the c-peptide or antibody tests for them to approve certain treatments. All the more reason to get them done to make best choice of treatment and improve chance of insurance covering costs.


I’ve said this before but it is SO infuriating to me that the whole “Type 1” “Type 2” terminology was introduced in order to break the erroneous association between age and diagnosis for what used to go by the name of “juvenile” diabetes, and yet STILL we get “You can’t have Type 1, you’re too old!” Such a stubborn association to break. Even my dx-ing dr knew this in 1983, just a GP but I guess he kept up with things, lucky for me.


An important one is how little we know about (all varieties) diabetes mellitus. We (research scientists) are constantly discovering new antibodies associated with T1, new metabolic mechanisms affecting different varieties of diabetes, etc.

“Type 1 (including LADA and other adult onset) diabetes mellitus” is still a medical description of symptoms and clinical signs (as are most diseases, but that’s a different discussion), and from a biological perspective almost certainly involves several (to many) different disease causes, progressions, and even outcomes. How do we know this? Because of all the different antibodies that have been discovered to date associated with T1, and because of the existence of “Type 1b” (also called “idiopathic T1”) diabetics, who test positive for no known antibodies and yet have all the clinical signs and symptoms of Type 1.

To a certain way of thinking, if someone doesn’t have DKA and is not positive for anti-GAD65, then they are not Type 1. This is, of course, ridiculous, and yet that is what my doctor told me five years ago. “You cannot be Type 1, you are too old and don’t have anti-GAD. Therefore, you are Type 2.” I fired that doctor, but it isn’t uncommon for GPs and PCPs to use this line of reasoning.

Type 1, Type 2, MODY, Type 3, etc. are all just labels for constellations of symptoms and test results (including antibody tests), and the underlying causation is not known. Some people with extraordinarily high serum anti-GAD65 (and 67) antibodies develop other autoimmune disorders (like mine, Stiff Person Syndrome) but never develop diabetes. So, high levels of anti-GAD do not cause Type 1 diabetes. Presence of testable antibodies are one of the tools used to diagnose Type 1 diabetes, but they are primarily used clinically to confirm diagnosis based on clinical signs or to differentiate “LADA” from “Type 2s” when oral meds don’t work the way a GP expected them to.

Sorry, don’t have time this morning for sources and further thoughts. I’ve written about these topics (from both a research scientist’s and diabetic’s perspective) before here, and I certainly have plenty of thoughts on the topic. Most of the thoughts come down to something very, very simple: we just don’t understand the diseases of diabetes mellitus very well, so for scientists and doctors, we can only do the best we can. Which sometimes (say, pre-1920s) wasn’t very well at all. And sometimes, today, it still isn’t very well at all.


Thanks for posting this. I wonder if racialization also plays a part in this phenomenon. Arleen Tuchman describes assumptions about diabetes based on race. For example, at the turn of the last century, diabetes was described as a “Jewish malady”, because of the bigotry that said Jews interbred, were nervous, etc. Then it was a disease of the middle class, aka white people. There is also an assumption that BIPOC only get Type 2 (which you touch on) which seems to be rooted in a bias that Type 2 is caused by slothful “lifestyles as well as racism. These views also affect the medical profession.

Here’s a link to a review of Tuchman’s book which you may find of interest. https://medicalhealthhumanities.com/2020/12/13/a-review-of-diabetes-a-history-of-race-disease/


What is MODY?

Here is a pretty good explanation:

Maturity Onset Diabetes of the Young ( MODY ) is an inherited form of diabetes mellitus. It is caused by a change in one of eleven genes. Up to 5% of all diabetes cases may be due to MODY . Just like other people with diabetes , people with MODY have trouble regulating their blood sugar levels.


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Hi Melitta,
You’re work here and articles were what got me through my type 2 to type 1 misdiagnosis 10 years ago!!! I was dxd with gestational diabetes in my 3rd pregnancy over 11 years ago and after that never went back to having “normal” BG levels. It was such a confusing and horrible two years afterwards trying to figure out what was going on with my body. I’ve had so much help and support here at tudiabetes. I’m grateful for all you’ve done being our “voice.”


I just wonder why a C Peptide test isn’t done for any diabetes diagnosis? I’ve been a T1D since 1965 and I was still required to take one (two actually) to get an insulin pump and Dexcom on Medicare. Maybe the word isn’t getting out to the whole medical community. Quite a few medical professionals just hand newly diagnosed diabetics a traditional diabetic diet plan and a prescription for Metformin and tell the patient to stick their fingers for blood tests once a day and boom, they’re done. The patient is diagnosed with “sugar diabetes”.

In my book, that’s just too simplistic to really work for anyone no matter what type or stage of diabetes the patient has.

I will say as one of the “skinny T1Ds”, blood sugar management, even with the latest tools can be a real struggle.