Siblings and Type

Hello all

I am a LADA who was misdiagnosed Type 2 two years ago at age 58. (fbg was 325 and I had all the symptoms but no dka). My brother is 3 years older and is pre-diabetic with a rising A1C (now 6.0). He has excellent insurance so this was picked up with testing at an early stage. Thing is he had gained some weight as he got older and was told to cut his carbs, fat, etc and lose weight. He lost 40 pounds and though he did make significant dietary changes it seemed a bit too easy to me for someone his age. He is now at goal weight and off the diet but continues to lose weight. The dietician told him something about his metabolism needing to adjust but I wonder about his Type and encouraged him to get c-peptide and GAD testing. (hyperthyroidism, which I also suffered from is another possibility but I don't think he has the other symptoms).

So my question is does anyone know (or have you experienced) if there is a genetic likelihood that siblings would have the same Type? It seems to me I have heard that many of us with diabetes have family members who also have diabetes but the type seems pretty random? I don't want to project my own experience onto my brother but there are striking similarities (aside from the stage of progression) right down to the exact amount of weight we each lost...40 without trying at all.


Hi Zoe,

I don’t know about the overall stats, but here are my family stats: my sister was dx Type 1 at age 10. Then my dad dx Type 2 in his 40s. Then I was dx Type 1 almost a year ago, at age 31. So clearly, my sister and I are genetically predisposed to Type 1. No one else in the family has it, but a lot of my dad’s cousins also have Type 2.

Thanks, Kate. Yes, it’s really sounding to me like diabetes runs in families but can be either type.

I don’t know the answer to your question, but I am a type 1 (diagnosed at age 21). My dad was diagnosed with type 2 a couple years ago and I often wonder if he is LADA and I am watching carefully for the signs.

He is doing fine on oral meds, diet and exercise now, but I remind him to have the endo test his c-peptide level…

Hi Zoe: I don’t know the answer, but have read various stats over time. Here’s one: If one child in a family has type 1 diabetes, siblings have about a 1 in 10 risk of developing it by age 50. Keep in mind, the stats for Type 1 diabetes and risk for family members EXCLUDE LADAs even though they are Type 1s (LADAs are still lumped in the stats for T2s, illogical as that is). So the probability is higher than 1 in 10 risk.

Hi Zoe,

I don’t know the answer. But i do have a sibling who is also T1 like me. He was dx’d as a young boy, and I was dx’d many years later as a young adult. Our grandmother was a T1 also. There was never a question as to our type. I sure hope that Melitta’s statistics are not a sure thing as there are 4 more siblings that do not have any type of D. I am beginning to question the ability to properly dx PWDs these days as I read more and more misdiagnosis happens.

I actually think diagnosis of type is fairly simple most of the time. When I was first diagnosed I had had been steadily losing weight without trying (and at my age that just doesn’t happen!), and I had another autoimmune disease, Graves disease. Those things should have been a red flag to do c-peptide and antibody testing at which point my diagnosis would have been clear. When I continued to lose weight (total of 40 pounds) and my oral meds stopped working despite numerous changes with steadily climbing blood sugars at a year and a couple months that should have been the second red flag to do testing for Type.

I don’t think doctors lack the ability to properly diagnose Type. They are just lazy and willing to go with outdated stereotypes: In my case, age 58= Type 2.