Type 1 antibody/c-pep tests and Medicare

I’m increasingly nervous about this, having just turned 65. I was dx’d in 1983 (“diabetes mellitus–juvenile type” as they called it back then), when these tests were not routine, and I never had them until just a few years ago when I started with a new endocrinologist. My C-Pep came in at the low end but not zero, indicating I have some “beta cell reserve,” and my GAD65 was negative. I gather that the antibody test isn’t very conclusive after nearly 40 years, but still, I don’t know if any such considerations matter when all you’re doing is checking off a box in a form somewhere. So… am I going to get disqualified for insulin and pump supplies? Any one else have experience with this?

When I became eligible for Medicare, eligibility for Medicare Part B coverage of insulin pump supplies required me to document a C-peptide showing a low level. Once submitted, Medicare does not require this to ever be performed again. It seems silly after living with T1D for decades but it’s a small inconvenience for this crucial supply. Medicare never required me to show any antibody tests.

Since I also pay a monthly Medicare supplement insurance premium (a supplement to traditional Medicare, not Medicare Advantage), I receive insulin pump supplies, insulin, and CGM supplies with no out-of-pocket payment under Medicare Part B.


But what counts as “low”? Mine’s above the minimum in the “normal” range.

C - peptide levels . Medicare defines insulinopenia 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.

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At worst case, you would need to go under Part D, but your CGM monthly bill would be covered under Part B. You would also then qualify for $35/month insulin which may make it cheaper to pay out of pocket for the insulin along with Part D coverage which is about $17/month. Take a look at your total cost (Insurance Premium + Insulin) and you may find that paying out of pocket is less. I am MDI, so that is the plan I am on and am in the same or similar boat with a “low C-Peptide” I don’t remember the exact value but can look it up it it is critical.

From WEbMD:

A normal C-peptide range is 0.5 to 2.0 nanograms per milliliter.

So that means that Medicare wants to see your C-peptide measured at <= 0.55 ng/mL (0.5 x 110%). My last C-peptide came in at < 0.1 ng/mL, the lowest level measurable by this lab test.

By the way, Medicare also requires a concurrent plasma glucose be measured along with the C-peptide.

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You don’t need an antibody test for Medicare. I have never had one. I had my first c-peptide ever when I went on Medicare to get approval for pump supplies. Like @Terry4 I got the lowest possible result at < 0.1 mg/mL. (Actually it is not the lowest possible result because Joslin has used more sensitive tests than the average lab to document minute insulin production by many longtime T1’s.)

Also as @Terry4 says, if you use diabetes tech, in most cases you are best off with Basic Medicare and a Supplement Plan. I pay higher monthly premiums than an Advantage Plan but I have no OOP costs.


I think mine was .04. After more than 53 years w/ t1, I cheered for the one or 2 beta cells still alive


Mine is either not detectable or less that 0.1 depending on the test method.
I am pretty certain that I don’t make any at all.

However the longer you fast the lower your result will be.
So if you are taking a test for Medicare I suggest a long 18 hour fast if you can manage that.

Keep your sugars as low as you can safely.
If you have some beta cells you don’t want them to have a reason to produce insulin and therefore c peptide.

Your beta cells create pro insulin. Then this breaks up into one molecule of insulin and one of cpeptide. So if you reduce insulin you reduce cpeptide.
More accurately if you reduce pro insulin you reduce both.
Beta cells are activated by high levels of glucose. So reduce glucose. Reduce the whole thing


Neither of my tests was done while fasting, so there’s that.

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I had to go through the C-Peptide test when I first went on Medicare. I’d been on a pump for 22 years at that point.

One tip someone gave me, especially for T2’s…make sure your bg is super low (not dangerously so, but in the 70’s or 80’s) at the time of the test. For some reason, if our bg is high, the C-peptide will test higher. I have a wonderful doc and when my first test was too high, he said, “take it again, I won’t submit this one.” And a friend on another D board told me about making sure my bg is low when I take the C-peptide. It worked, and I qualified.

I also had all the antibody tests done at my own expense, because I don’t think they were done when I was diagnosed in 1984 at the age of 38. Fortunately or unfortunately, I didn’t show any antibodies, but after 27 years with D, who knows if they’d still show up? So, I’m still classified as T2 (plus, I absolutely NEVER produce ketones).

Good luck, Dr. BB…Medicare coverage is fairly decent, but we definitely have to jump through many hoops to get it.

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When I came on Medicare did not require a C-pep or GAD65 test. Now that was 12 years ago when I was 51 because of disability. They have paid for insulin and pumps since.


I went on traditional Medicare 6 years ago. Despite being T1D for now 49 years and, thankfully, still counting, my one and only C-peptide test was for Medicare coverage. Like others here, I was “lucky enough” to get a result of < 0.1 so there was no question about coverage. It is a strange world, indeed, where we hope for what most would consider to be a “bad” result in order to qualify for insurance coverage …

However, in this case, I like @Timothy’s suggestion as to how to legitimately make your C-peptide return as low a value as possible.

As a child of the sixties, this causes me to think of all of the urban legends as to how to FAIL your induction physical. In the category of “a day late and a dollar short”, I developed T1D 18 months after passing my induction physical. I wasn’t actually drafted, and didn’t even do that by sitting on the “Group W” bench for you Arlo Guthrie aficionados.

Good luck, @DrBB … may your C-peptide come back low!



I don’t think it has to be 0. Mine at dka diagnosis in 2012 was .4 with a range of 1.1 - 4.4. About 2 months later I had my endo test again and it was lower, I think .2. I was hoping it was all a mistake still.

When I did the test for Dr Faustman’s research it was even lower, I can’t remember, maybe .022. They had a very sensitive test and also tested for t cells specific to type 1 which kill off beta cells which I had.

My gad- 65 at diagnosis in dka was 34 with a range of .0-1.5. I don’t know if they tested that at the Faustman lab or not and I haven’t had it tested again. I heard like you said after many years of type1 it is often negative.

Crazy we have to go through this crap after everything else. I hope it works out, sounds like your c peptide is low enough.

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I didn’t get T1 until I was 28, but I lotteried at 296 anyway and then the draft ended. Wouldn’t likely have been called up unless WWIII broke out.

Now that I am on an insulin pump, my c-peptide most always comes back as < 0.01. However, in the past, when I had A1c results showing > 8, my c-peptide would occasionally come back up to 0.6. Apparently, when under the strain of elevated BGs my pancreas will produce some insulin, but not enough to reduce my BGs.

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beta cell cheer block Give me a B, Give me a E, Give me a T, Give me an A whats that spell BETA what do we want BETA Cells what do we want BETA Cells what do we , oops

never mind.


Medicare does require that the C-Peptide test be a fasting test. My permission to receive my ongoing CGM, pump and pump supplies were delayed until my Doctor re-sent the C-Peptide and glucose test results with an added statement verifying that these were fasting test results.

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Yeah, my c-Peptide test for medicare was the third C-Peptide test I have had done. The first, many many years ago was .003. The one when I started with my first endocrinologist where I live now - in 2004 - was .001. The one I had done last Spring for Medicare was <.1 . My pancreas doesn’t produce any insulin, nor does it have any exocrine functions as well - no digestive enzymes, no alkalinizing function. It makes a great placeholder in my abdomen but not much else.

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I’m curious as to why Medicare requires the c-peptide test to be during fasting. My doctor gave me one so that I could qualify for a pump but it was not a fasting test (came back at < 0.01). I mentioned to him after the fact that I read Medicare states the test should be a fasting test and he said if its at 0 while not fasting it will certainly be there while fasting. Now I’m thinking Medicare will have a problem with this as I’m still in the process of trying to get a pump.