What is a C-Peptide test for? (What time of day is best to get C-Peptide test)

composition of tools for blood sugar measurements

written by Nina Shantel, blog: RealDietHelp.com, published November 14, 2023

A C-Peptide test determines how much insulin your pancreatic beta cells are producing. Most doctors have patients take this test in the morning while fasting, but this is a mistake because a morning C-peptide test while fasting is when the lowest amount of insulin your body is producing, ie. there is no reason for your pancreatic beta cells to produce insulin during a fast.

It may be best to take a C-Peptide test around lunch time after a meal containing a significant amount of carbohydrates from whole foods with less diabetes medication so that your pancreas will be prompted to produce insulin to lower your blood glucose level. (Consult with your doctor to determine how to do this safely).

When I took a C-Peptide test after fasting overnight, test results shown in the video below, the number was a low .59, so my doctor told me I’m no longer a Type 1.5 diabetic, but a Type-1 diabetic, which was distressing news.

When I asked my doctor to order another C-Peptide test to see if my beta cells are able to produce more insulin after a meal containing potatoes and using 1 less unit of insulin, I was happy to see that my beta cells were secreting an adequate about of insulin, proven by the test number of 1.55. With the updated results, my doctor said that I’m actually a Type 1.5 diabetic because I am able to produce insulin on my own, but that I still need insulin injections because my body is producing autoantibodies to attack my pancreatic beta cells.

This is not just a weird phenomenon. A client diagnosed with Type-2 diabetes that I have been working with had C-Peptide fasting results under 1 ng/mL (low), and his non-fasting C-Peptide is 3.12 ng/mL (high).

After your results come in, and if your C- peptide is high, you want to find out why your body is producing so much insulin. Some explanations for a high output of insulin is being overweight and/or eating a diet high in saturated fats. The saturated fats you want to eliminate are dairy, oils, and animal protein, as these are disease promoting foods, and the very foods that trigger insulin resistance, diabetes and heart disease.

It’s important to determine if you are a Type-1 or Type-2 diabetic because the type of medication differs, depending on diagnosis; you want to make sure that you are taking the appropriate medication. “…type 1.5 diabetes has characteristics of both type 1 and type 2 diabetes and is often misdiagnosed as type 2 diabetes. As a result many people living with type 1.5 diabetes are treated with ineffective oral medications to control their blood glucose even though the most effective course of treatment involves the use of basal and/or bolus insulin…” (2).

The five antibody tests to confirm Type-1 or Type-1.5 diabetes are: GAD, ICA, IAA, IA-2A and Zn-T8A (2). Make sure to have your doctor order all five of these tests to rule out Type-1 diabetes.

The type of diet a Type-1 diabetic and Type-2 diabetic should eat differs too. The type of diet a Type-2 diabetic should eat is a low fat, oil-free, plant-based vegan diet because this diet doesn’t just manage the disease, it’s been shown to reverse Type-2 diabetes.

If a person has Type-1 diabetes or Type 1.5 diabetes, confirmed with positive autoimmune antibody test results, the Type-1 diabetic should try Dr. Brooke Goldner‘s GAIP raw vegan autoimmune protocol to see if beta cell destruction can be stopped in its tracks, and possibly be reversed. The other benefits of Dr. Goldner’s dietary protocol is improved overall health and fewer insulin injections.

I have been eating a whole-food plant-based vegan diet for over three years and love baked, stir-fried, and simmered (cooked) plant foods, but the pain from Raynaud’s, erythromelalgia, autoimmune hives, anemia, poor circulation, sun sensitivity, and dry skin, pushed me to try Dr. Brooke Golder’s GAIP raw vegan autoimmune reversal protocol.

I was diagnosed with Type 1.5 diabetes over 17 years ago (later diagnosed as Type-1) and have been on insulin for over 16 years. I had two doctors tell me to try Dr. Brooke Goldner’s program since I am a Type-1 diabetic, not suitable for water fasting, in chronic pain from several autoimmune conditions and am highly motivated to take action, even if it means saying goodbye to my favorite foods.

On Dr. Goldner’s strictest plan, I have been able to reduce my insulin from 15 units a day to just 3 units of insulin a day. The other good news is that my pain, erythromelalgia and autoimmune hives are gone. These great results are from just 8 weeks on Dr. Goldner’s GAIP plan. (See 1-minute video below, which shows my before and after photos after 6-weeks on the GAIP protocol developed by Dr. Brooker Goldner and her husband).

Changing one’s diet is the hardest accomplishments in my life and I’m ecstatic that I did it. I feel fantastic and happier than ever. I miss burgers, fries, brownies, sweet potatoes, and many other foods, and do feel a little sad when I see or smell these foods, but I won’t risk my health just to eat something tasty because feeling good and being able to DO THINGS is so much more important to me.

P.S. Once symptoms are gone on Dr. Goldner’s raw vegan detox, cooked foods can be added back, one at a time for three days to see if that food causes symptoms. After five months on Dr. Brooke Goldner’s GAIP protocol, my symptoms are gone! I have been adding back cooked foods and found that I cannot eat garbanzo beans without foot pain. See video below for before and after photos and details.


1. Discussion with plant-based specialist, Dr. Michael Klapper

2. Khambatta, Cyrus, et al. Mastering Diabetes: The Revolutionary Method to Reverse Insulin Resistance Permanently in Type 1, Type 1.5, Type 2, Prediabetes, and Gestational Diabetes. Avery, an Imprint of Penguin Random House, 2022. Pg 190-192.

If this post is located on any other website other than mine, which is RealDietHelp.com, it’s been unauthorized, plagiarized (copied without my permission). The other social media sites where my articles and videos are approved to be published are on my YouTube channel (Nina’s Nutrition & Exercise Videos), my Fit Girl Facebook page https://www.facebook.com/TheHighFiveDiet/ and my Twitter account https://twitter.com/medairyfree

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