C-peptide/mixed meal challenge results - what do they mean?

As part of my abortive attempt to join the teplizumab study, I was given a mixed meal challenge - essentially, have 2.5 cans of a canned milkshake-type product and then have blood drawn for c-peptide and BG testing. Since I’m very solidly in (what I think) is honeymoon, I knew that my sugars would come under control, but what was interesting was the c-peptide results.

It should be noted that the “normal” range for this lab is 1.1-5 ng/mL.

Baseline (10 minutes pre-drink) was 2.3. This was a 10 hour fasting mark. Half an hour in, I was up to 4.4 and then went up into the 5.8-8.1 range for the next 2 hours. Normal c-peptides didn’t return until the 3:30 mark from drinking.

Blood sugar spiked, with highest mark at 2 hours, and then was back to normal by the 3 hour mark, and actually down to 69 by the 4 hour mark.

Am currently taking 6U Lantus at night, on very low-carb diet, and adding much exercise, with concommitant good control of sugars - I think the highest I’ve seen in the last 2 weeks other than during the mixed meal challenge was around 145, and for the last week I’ve been running mostly in the 70s and 80s during the day, with virtually no readings above 100.

I should also note that I reduced my Lantus to 4U the night before the test. Had an essentially unchanged fasting blood sugar (have been bouncing in the 110-130 range for fastings.)

Obviously, I’m going to take these numbers to my endo, but does anyone have any thoughts?

If you are still making insulin and you have a high blood sugar, your body responds by producing a lot of insulin to bring that down. That would be my guess why your c-peptide was so high. But i don’t understand the whole process either…

The nice thing about parents who are doctors is that you can run this by them - my mom thought the #s looked pretty strange, more like an insulin resistance than a lack of production. This was based on the “normal” levels before and at the end of the test. She did say that this is out of her realm of expertise, however.

Who knows?

Insulin resistance is possible or low first phase insulin production which leads to high blood sugar and high second phase insulin production (reaction to high blood sugar). OK, this is not my realm of expertise either… just thinking “out loud”

This is classic insulin resistance. This is called hyperinsulinemia. It is important to maintain normal BS in order to slow the destruction of Beta cells.
Best health
danny weems

I agree. Sounds like impaired first phase and solid second phase. The low at 4 hours means that you are insulin sensitive, not resistant. I responded similarly to the glucose tolerance test- spiked high, produced a ton of insulin and crashed down to 50 after 4 hours. I take 5U Levemir at night and manage without fast acting insulin by low carbing, so we are probably in the same situation regarding the honeymoon phase. I hope to still produce insulin for a long time to come.

Libby –

At diagnosis, did you have ketones in your urine? That and anti-islet antibodies seems to point my situation to T1, but what you’re describing (and your diagnosis) seem otherwise.


No, my BG was not very high at diagnosis. But I do have islet cell antibodies so I have LADA (Type 1 for grown-ups or Juvenile Diabetes according to my insurance. At age 54 that makes me chuckle.) My A1C was only 7.2 when I was diagnosed and my antibody levels were just on the edge of positive so I think I was lucky to catch this at a very early stage.