C Peptide

I’m on Medicare and I have a supplement from Anthem . They are requiring me to have a c peptide test before they will cover my pump supplies. The last time I had a c peptide test was about 5 years ago and I was told to hold my insulin injections before the test so at that time my BG was sky high and and my c peptide was less than 1. This time I’m told to continue wearing my Insulin pump and that there is no need to fast. I’m afraid that if I’m just less than one like .7-.9 that my insurance won’t cover me for the supplies.
I’ve been a diabetic for 12 years and I’ve had the pump for 3 years, and it has saved my life. What is the best way to insure a low reading below .6? Should I go ahead and fast the night before the test or should I eat? I’m just really scared that it won’t be low enough for me to be covered.
Thank you in advance for any suggestions

I went on Medicare about 4 years ago and they do require a C-peptide. I don’t know what the preparation was before I had to get my test but I was also told to continue to wear my pump. As a T1 we are never to be without insulin.

No idea why you were told to hold your insulin injections! The modern insulins we use do not contain c-peptide, so would have no influence over your reading. It will be what it will be. I’m pretty mind boggled that they would base your pump on a c-peptide. I’ve heard of pumps being based on A1C, but ironically I have heard people being told they were too high AND that they were too low. It’s nonsense. I also have Anthem. I did a A1C test before I got my pump but I wasn’t told it would matter in the approval. My guess is your reading will be significantly less than 5 years ago, but there really isn’t anything you can do to adjust it as far as I know.

@Zoe - Medicare has different rules when it comes to approving pumps. I was on a pump for years and when I became eligible for Medicare I had to go through what Mary is asked to do…Medicare is a whole different ballgame when it comes to Diabetes.

I haven’t really checked into medicare yet because I have 3 years, but do those rules apply if you have another insurance? I’ll continue to use the CalPers insurance I have now and just register for medicare becase I have to.
I’m not worried though because my c-peptide was low 2 years ago!

I remember a post on another formum about this. This person was approaching 65 and was on an insulin pump with great control. He wanted to see if his C Peptide would qualify. He actually ate way more carbs than normal with less insulin to see if he could get the results low enough. He didn’t. I still have 4 more years to go so don’t know the ins and outs of supplemental. But isn’t this why we get the supplemental on top of Medicare.

Perhaps the more scientific people among us will comment, but I wouldn’t think eating a lot of carbs with less insulin (basically driving blood sugars up) would do anything for c-peptide! C-peptide is a by-product of the insulin our bodies still produce (or don’t!). I don’t think high blood sugar would influence that.

Yes, I’m not sure I understand this Jeannie, and I am like you not quite there yet. But I think very few people are able to manage with just plain Medicare, without a supplemental. But I have no clue if “supplementals” also have that requirement. For me Medicare will not be my primary but my current insurance which I have for life will. (lucky me, I know-smartest thing I ever did, working for a County for 5 years to get CalPers insurance) and I know that covers the pump. If it didn’t I could see being anxious about it. But bottom line so many things could change in a few years such as medicare (for the worse?) and pump requirements (for the better, I think, as the pump begins to be thought of as more the Standard of Care, rather than something you need due to certain cirumstances)

Except Zoe is correct in that Medicare does not require someone to not take insulin - I took insulin the morning I did my c-peptide and Medicare approved my pump.

I am not sure who told you not to fast, but the Medicare requirements state that the c-peptide has to be done fasting. Scroll down to page 126 of the CMS Manual – the c-peptide stuff starts at section 280.14. Your BS also has to be below 225.


I took my insulin the morning of my test. I asked about that and was told it was OK. I also Googled and injected insulin has no effect on the c-peptide results.

Zoe, I can’t remember the scientific details, but I do remember this conversation coming up on another board about the BS & c-peptide. For a T1, a high BS won’t have any impact on the c-peptide but for a T2, it can lower it. That is why Medicare added the clause that BS has to be below 225 for their c-peptide.

If your Medicare ends up paying any portion of your supplies, then you would have to follow Medicare guidelines. But like you said, if your c-peptide qualifies, then you have nothing to worry about.

As Kelly mentioned above, injected insulin and c-peptide are unrelated. Your c-peptide being lower is simply, as you said, indicative of your producing less insulin now.

Thanks for the info about medicare, Kelly. I don’t know if Medicare will pay for any of my supplies as my calpers insurance is much better, but maybe medicare pays and then my other insurance pays what they don’t cover, but yes, for me, the argument is moot.

This is the first though, I’ve heard of c-peptide requirements rather than A1C (which seems very arbitrary as some people are told it needs to be high (to show need of better care) or it needs to be low (to show good management pre-pump).

Just out of curiosity what is the c-peptide requirement? Oh, I see, Mary Ann said below .60?

Don’t eat carbs before you go for the test. Possibly fasting could be good. Try to get your BGin the normal range before the test. High would not be good as it might stimulate your pancreas.

Fasting is actually required for Medicare - I posted the link to the CMS manual above. Medicare won’t accept the test if it is not done fasting.

Medicare won’t pay for a pump or supplies for T2s so the c-peptide is their way of weeding T2s out. I have read about a lot of people that had pumps for years and then when they went on Medicare, could not get their supplies and had to go back to MDI. There are some other requirements but that is the big one everyone sweats. If you have a high A1c or suffer from a lot of lows, you still have to meet the c-peptide requirements.

Here is the requirement from the link I posted above:

Updated fasting C-peptide testing requirement:

• Insulinopenia is defined as a fasting C-peptide level that is less than or equal to 110% of the lower limit of normal of the laboratory’s measurement method.

• For patients with renal insufficiency and creatinine clearance (actual or calculated from age, gender, weight, and serum creatinine) ≤50 ml/minute, insulinopenia is defined as a fasting C-peptide level that is less than or equal to 200% of the lower limit of normal of the laboratory’s measurement method.

• Fasting C-peptide levels will only be considered valid with a concurrently obtained fasting glucose ≤225 mg/dL.

Maybe I am being dense here (happens quite frequently) but how could they tell if you are fasting or not?

Normally the lab tech will ask - if she says no & it gets marked down as no (or even not marked at all), it will get rejected. There is no way to prove whether you had food or not, but the question will be asked. If she goes in at 5 in the afternoon, they would probably question whether she was actually fasting or not.

Yeah I went to get a lipid panel done on a day I was basal testing and me and the lab guy got into a bit of a dispute about whether I was indeed fasting. It came down to regardless if I was fasting or not I wanted the test done NOW!

Interesting! Doesn’t the c-peptide of Type 2’s also decrease over time when their pancreas finally stops producing much of its own insulin (I thought that was the reason Type 2’s are put on insulin eventually). I wonder if Medicare would pay for a Type 2 who didn’t produce much insulin anymore? Maybe I shouldn’t try to make Medicare rules make sense. I worked for County BH for a few years, where I thought of myself as working for Behavioral Health clients not for “the government”. Every once in awhile I would ask a coworker what sense a certain county regulation made. Her answer was often, “Zoe, it’s the government” which explained everything. (or not)

Yes Medicare will pay for pump/supplies for anyone that meets the above guidelines regardless of Type.