C Peptide......confused

Caz_B

Well-Known Member
Messages
70
Type of diabetes
Type 2
My GP sent for a the C Peptide blood test to find out if i am actually Adult Type 1 as opposed to Type 2. The first blood test came back insufficient sample so i was for another blood test. This one has come back stating 'cannot test due to glucose something or other missing' or something along those lines. This GP is not the GP at thr Surgery who us the specialist in Diabetes so it would appear she is missing something. Has anyone who has had this test got any idea what the GP is missing? Thanks
 

Caz_B

Well-Known Member
Messages
70
Type of diabetes
Type 2
Should this be a fasting test? Also do you have to stop taking any diabetic medication (tablets) x
 

Caz_B

Well-Known Member
Messages
70
Type of diabetes
Type 2
Reading on the internet it should be a fasting test and meds stopped in order to do the test. Also a shot of glucagon given in between two blood samples. Xx
 
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catapillar

Well-Known Member
Messages
3,390
Type of diabetes
Type 1
Treatment type
Insulin
A cpeptide test doesn't need to be fasting. It certainly doesn't need a shot of glucagon. I've had a couple of cpeptide blood tests, there was no fasting and no stopping medication (because i kinda need my insulin to stay alive) and I definitely would have declined if they told me they were going to give me glucagon for the test (because there are occasions when I need that to keep me alive too and it doesn't work if you've had an unnecessary shot of glucagon for a cpeptide test in the previous 24-48hrs, and it makes you feel sick and hyper). I've also done urinary cpeptide tests - there were definitely strict instructions to follow about what pee after eating they wanted for that.

A cpeptide test won't tell you if you are adult onset type 1. All it tells you is if you are producing insulin and how much. If you are producing a lot of insulin that would point to type 2. If you are producing low levels of insulin it doesn't do anything to tell you why you are producing low levels of insulin and so it doesn't do anything to tell you what sore of diabetes you have. A type 2 diabetic can be producing low levels because their beta cells get worn out by hyperinsulimia. A type 1 diabetic would be producing low levels of insulin because their immune system is killing off their beta cells.

The only test that can give a definitive answer of type of diabetes is antibody testing to see if you have the antibodies associated with autoimmune type 1. If you are antibody positive and diabetic you are definitely type 1. However, antibody negative doesn't mean you aren't type 1 as 25% of type 1s are GAD negative.
 
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Caz_B

Well-Known Member
Messages
70
Type of diabetes
Type 2
Going to ring and speak to the Diabetic GP on Tuesday as i have now had two blood tests that have proved totally useless. Whatever the correct test is they are meant to be testing to see if i am LADA as opposed to Type 2. After being able to control my diabetes by diet when diagnosed two years ago recently despite eating hardly any carbs i was getting constant high readings and no matter what i ate could nit get them down. My 3 month Hba1c was higher than when diagnosed. Metformin does nothing but when the GP has put me on Gliclazide it has brought it down although my fasting reading when i get up is still 12 and above. I then take the Gliclazide and my readings drop. X
 

Daibell

Master
Messages
12,642
Type of diabetes
LADA
Treatment type
Insulin
Hi. I had my c-peptide done privately and it was fasting but no glucagon; I've never heard of that? There are some arguments out there about fasting or non-fasting for c-peptide but I think fasting is the norm. If Gliclazide does reduce your blood sugar then you do have at least some working beta cells left. Before I went onto insulin I was on full dose (320mg) Gliclazide which had no effect whatsoever which told me it was time for insulin and my c-peptide was right at the bottom of the 'within range'. I largely go along with the @catapillar post but as she knows I would put a slightly different take on how you define T1. It is true that T1 and LADA are defined as an auto immune disease where the beta cells are destroyed by antibodies hence the test for GAD and a few other antibody types (there are several). Although long-term hyperinsulimia can destroy beta cells that was not true in my case or for many others. There are other causes of beta cell death such as viruses. The end result is the same as LADA except the cause is other than anti-bodies. I call this LADA - others would place me in the T2 group which is not helpful. There have been recent press articles about the degree of mis-diagnosis amongst slim adults who are in essence LADA thru beta cell death. However you label it, it needs insulin treatment eventually and managed in the same way as any other 'T1' but there may be a honeymoon period of slow beta cell death which I went thru. I hope you do get your c-peptide test done and bear in mind the honeymoon period of months thru years can determine when insulin should be started if it shows a low natural insulin level.
 

TheBigNewt

Well-Known Member
Messages
1,167
Type of diabetes
Type 1
Treatment type
Insulin
Actual insulin levels can be measured and are probably the most accurate method. However we Type 1's can't really stop taking exogenous (injected) insulin so the C peptide gets around that and doesn't figure in insulin you injected just insulin you make. I'm not sure how accurate it is either (ie what's the standard error in a single specimen?).
 

shezza48

Member
Messages
18
Type of diabetes
Type 2
Treatment type
Insulin
I’ve never had a C peptide test, think I’m going to have to have one soon, blood sugar levels are all over the place, sometimes it’s above 27, other times it’s as low as 2 or 3. I control my carb intake, I have now got to take more novorapid before food than I used to. I’m having lots of hypos, mainly first thing in the morning but I’m now having them in the day too( had to have emergency glucose in post office queue last week as Dexcom said blood sugars were low at 3.2. I’m self funding CGM) DSN wants to change my long acting insulin from humulin I to I think lantus. I’m currently looking into self funding an insulin pump as when I was in hospital with my pulmonary embolism and I was in ICU I was on pumped insulin, 4 units every hour, blood sugars never really rose or went low even after food, now my levels are so unpredictable. I now have to carry a hypo kit, I take 1500 mg metformin prolonged release, I was on gliclazide but got took off it over a year ago. Having such unpredictable glucose levels makes me not want to go out on my own. I’m waking up probably 5 mornings out of 7 with blood sugar levels of between 2 and 3, it’s getting me so down now. Got appointment with DSN on February 15th, hoping she can sort these hypos out.