C Peptide

I just had my C Peptide retested and here are the results:

June 2010: C Peptide 3.4 (range 1.1-4.4) BGL 91 (low carbing for 3 months before this test was done on 34 units Lantus) A1c: 6.3
August 2011: C Peptide 0.8 ( range 1.1-4,4) BGL 75 (continued low carbing on 28 units Lantus)
Done at same lab. A1c: 5.3

Little background: Diagnosed end of March 2010 with bgl between 300-450. Started Lanus immediately to get bgl down before upcoming surgery. The year before I had a couple high bgl’s but the doctor though it was due to my thyroid cancer and the surgeries I was having at that time (25 years prior suffered with Hashimoto’s). Since diagnosis, I have gotten my a1c down to 5.3 through low carbing (30-50 gms a day). Lately I feel like I practically have to starve myself to keep my bgl’s down. At my doctor appt. (same day blood was taken but not all results were back), the doctor suggested going down on my Lantus since I was doing so well. I have since gone down to 22 units and my fasting bgl is about the same but I am spiking more and staying higher longer. I have an appt. with my endo in Sept. to get antibody testing as my doctor said he didn’t know much about the antibody testing. So, my question is, is my change in C Peptide significant or is it just the result of low carbing and Lantus? Any comments would be appreciated.

One more thing, during the last year I have lost 80 lbs through low carbing. I am thinking it really helped IR.

Hi Jest,

Congrats on the amazing A1c! From 6.3 to 5.3 is quite an accomplishment. That took a lot of dedication as did losing 80 lbs. Wow.

C-peptide is directly related to insulin production. T1s have extremely low C-peptide because of low or no natural insulin, T2s typically have a high C-peptide level because they produce a lot of insulin due to insulin resistance. Your test results show a marked decrease in C-peptide (a corresponding decrease in endogenous insulin) that points to T1 (LADA), as does more BG highs. This isn’t a result of Lantus & low carbing.

You shouldn’t have to starve & probably need to begin rapid acting insulin for meals. You’ll need less Lantus with bolus insulin. Continuing with low carb will keep your insulin doses & weight low.

Great that you have an appointment with an endo.

Thank you for your response. I asked this because some say that if your fasting bgl is normal or low normal and your c peptide is low that that doesn’t tell you anything…they say your bgl needs to be high. I have never been one with much of a dawn phenomenon so my fgl doesn’t ever really shoot up much when fasting. Perhaps because of my low carb diet I don’t have much glycogen stores and maybe the metformin also affects this. I just always thought it was so weird how I went from practically normal a1c and bgl up to bgl of 300-450 in about a two week time period prior to diagnosis. My a1c two weeks prior was at 6.3 or 6.4 (can’t remember exactly) to 7.9 in those two weeks. Luckily because of the upcoming surgery I was put on Lantus right away.

Great job. It takes a lot of dedication to make such dramatic changes and your A1c reflects your success. I think often, if you actually have T1(LADA) as an adult, you don’t lose insulin production all at once, over time it degrades. So it is very common to be given the diagnosis of the more common T2 and only after treatment fails and things get bad is the diagnosis of T1(LADA) considered. In the case of your c-peptide, it is kinda inconclusive, although it is low, your BS at the time was only 75 mg/dl and a low insulin/c-peptide would be expected. The real confirmation of insulin deficiency comes when your BS is high (like > 150-200 mg/dl) and you have a low c-peptide. In my case, my c-peptide was 1.8 with a BS of 130 mg/dl, and my endo still considered it inconclusive.

You may be concerned about highs, but it could also be your perspective. If you are higher than 140 mg/dl 2 hours after a meal, then you might say you are high. Are you seeing readings at that level?

I wasn’t until I went down on Lantus and now I am seeing 150’s to 180’s. And it takes a long time to come down.

I can’t comment on your question, but I have a question for you, could you give me
a idea of a type low “carb” day for you. I am on lantus up to 20 unit per day now and it is not working.
But I have not been low carbing either. Any help would be appreciated. Thanks.

Here's a couple of links to explore to see if low carb may be something you want to try. BloodSugar101 and the Bernstein Group here on tuD

I try to eat less than 30 gms of carbs a day but realistically that can’t happen everyday because of life so I do for sure stay under 50 gms a day. You probably have to adjust your Lantus up more.

So I saw my endo yesterday for my yearly thyroid scan (funny to scan when there is no thyroid–it was removed due to thyroid cancer) and I talked with her about my diabetes. She said I am her star patient in that area. She thinks my low carbing is great and I talked about how I really spiked one day when I ate 60 gms of carbs while eating out in one meal. She said that most of her patients say they can’t go as low as 60 gms of carbs at a meal ever! She said most of her diabetic patients don’t or won’t use diet in addition to meds for treatment. She said that is not good but that is the reality. She also said that when she gets a patient like me, she realizes that she has to be careful not to assume no one will listen or try when determining treatment. As far as the c peptide results, she said that since my bgl was were it was at, my c peptide would be lower. She did do a GADs test and results won’t be in until next week sometime. She said it wasn’t necessary as my treatment would be the same but if I was curious, she would do it. Also, she did say that there would be some merit in doing the test with my autoimmune history, especially in regards to Hashimotos. I will be glad to get the results so I know for sure, one way or the other. Like she said, either way right now, I probably wouldn’t do anything different with my treatment.