Sorry if this is a topic somewhere here. I recently retired and now am on Medicare and a supplemental insurance. I’m being required to do the C-peptide test AND a fasting glucose. The fasting glucose concerns me mostly as I’m a pump wearer. Do I turn my pump off? I’m concerned that my number be high enough. Any tips? Pointers?
I don’t know the requirement. And that’s why I’m asking here…if others know about this issue. I absolutely WOULD assume that my fasting with a pump would be too close to “normal.” So looking for input here.
Thy use your fasting glucose just to be sure you aren’t trying to defeat the test. Your cpeptide test indicates how much endogenous insulin your body is making, but if you take extra insulin, it will drive your endogenous insulin lower. So the test is only valid if you are in normal range60-120. If you are not in that range they will adjust.
I don’t know the formula.my cpeptide has been at zero for decades so I don’t think about it much, aim for 80 on your fasting . If you go too low your liver will dump glycogen and your body might try to make extra insulin to cover if you have any islets left, if you are high, then your islets will definitely be trying to produce. 80 is the sweet spot, your pancreas should be dormant at this level
Thanks for your answer. Let me be sure I understand your point regarding the fasting glucose being 80. Wouldn’t they be looking for a high glucose that would further support my need for a pump?
Also, what do you mean “they will adjust” with the c-peptide? I’m simply wanting to be sure that these one-time tests “prove” that I am truly in need of a pump (which I’ve been using for years now; but Medicare is asking for these tests).
You just need to have your doctor order both tests. Don’t overthink it. I went through this a year ago. I don’t remember the number exactly but I was wearing my pump and my fasting glucose was normal range.
Your fasting glucose it only a rule of thumb. A high glucose could drive the cpeptide higher so they will adjust the value of the cpeptide.
Really the cpeptide test was designed for type2 patients and fasting was a good way to get a baseline for how much insulin you make
For type 1 it’s drilling down on this same concept, but because we use insulin, the test can be thrown off by very low or very high fasting glucose.
So aim for 80, and aim for the same level every time you take the test so you can see an actual and dependable graph to see if you are losing islets or holding steady. If they see over a year that your cpeptide is decreasing but your fasting glucose is steady, they can determine you are losing islets and are more likely to approve you( really useful for LADA)
That’s only important if your c peptide is borderline, if it’s zero like most of us type 1, who were diagnosed young, we are at zero no matter what our fasting glucose is
This test is done to determine for Medicare that you are a type 1 and need a pump. C-peptide is the by-product and only made when your body makes it’s own insulin and it’s not made when we take outside insulin.
But a percentage of type 1’s still make some small amount of insulin. I don’t believe it matters at what age you got type 1 as Joslin has done research and found out that some long term type 1’s still make insulin. One theory today is after the initial assault on your pancreas, your body might recover some and be able to make some insulin. But the biggest problem becomes with Medicare is how much you still make. If you’re more recently diagnosed as an adult it can take years to fully stop making insulin, so that’s a problem and then add some people still make some insulin long term.
The fasting glucose is used from what I understand to make sure of the accuracy of the C-Peptide. Another test usually wanted is an antibody test. A positive is also the sign of being a type 1.
As mentioned above by @SophieCat, there is a whole discussion about the C-Peptide that supplies information you will find useful when @DrBB had the same issue.
I told my endo, hey maybe we have been wrong all along. I mean who knows with monkey mice they used back in 1974. Oh well, it turned out as she suspected. I told my wife, well, you know I have a new diaversary. Now I have three days to celebrate each day.
She promptly informed me, that she not ever going to buy me three presents. So much for number 4 when I was diagnosed with ED. Bummer.