• Guest, the forum is undergoing some upgrades and so the usual themes will be unavailable for a few days. In the meantime, you can use the forum like normal. We'd love to know what you think about the forum! Take the 2025 Survey »

Should C peptide be tested before starting medication?

Swiggy

Swiggy

Well-Known Member
I was referred to a hospital diabetes clinic and I have just spoken to a doctor who has suggested doubling Metformin dose to 4 tablets per day and adding a SGLT2 inhibitor because my hba1c has gone up from 59 to 79 since 2021.
In 2021 I had a c peptide test that the GP said showed that I was producing a very large amount of insulin, he didn't give me any figures but said it was three times what the higher end of normal was. I have been testing for the past 6 years and eating a low carb diet but I have lost no weight at all.
My GP suggested Victosza injections before COVID but when I told him that I had had a cyst on my pancreas as a child he said it wouldn't be suitable for me.
The doctor from the clinic was not aware of the cyst and has said that he suspects that my pancreas is not producing much insulin any more and that's why my blood sugar levels are increasing. I asked if I could have a c peptide test before starting to take more medication and he said that I should try the medication for three months and then see if it's needed.
I'm feeling scared and confused and I don't know whether I should pay for a c peptide test privately before taking the medication.
I'm not expecting any medical advice but has anyone else been in a similar situation?
 
I haven’t got much to offer, but I would have thought your GP would wish to confirm his theory that your pancreas is not producing much insulin anymore, with another C-peptide test. It’s a straight forward test. It would at least confirm or dismiss his theory and be in a better position when prescribing you the appropriate meds. I’m not a Dr, but that would be a big drop from producing 3 x the higher end of normal insulin to producing not much insulin.

I’m no expert, but surely if your pancreas was not producing much insulin your blood sugars would be higher .

It’s Always a personal choice whether or not to go private and get tested. If I was in your position and able to go private, I would want to know.
 
Thanks Melgar, I appreciate you taking time to reply. I'm going to tell my GP that I don't feel comfortable starting medication without testing to confirm that I'm not still producing too much insulin. Fingers crossed he orders the test.
 
You need to get your blood sugars down to avoid complications so the best advice is to follow your GP's advice on the medication. The results of a c-peptide test is not affected by Metformin. It could also be that you have become more insulin resistant over time which is causing your blood sugars to run higher.
 
ert said:
You need to get your blood sugars down to avoid complications so the best advice is to follow your GP's advice on the medication. The results of a c-peptide test is not affected by Metformin. It could also be that you have become more insulin resistant over time which is causing your blood sugars to run higher.
Click to expand...
Thank you, I have increased my Metformin after what the clinic doctor said yesterday and I'm waiting for my GP to prescribe the additional medication but I would like to speak to him about it. I appreciate you responding to me ert.
 
rubyparkfj said:
If you do not have financial problems, it is better to test your health in all areas before starting treatment
Click to expand...
This is a UK forum with the majority of members from the UK, all our health care is free & provided by the NHS, I am a little confused by your comment as you say you are in the UK, are you paying for your medication etc?
 
lovinglife said:
This is a UK forum with the majority of members from the UK, all our health care is free & provided by the NHS, I am a little confused by your comment as you say you are in the UK, are you paying for your medication etc?
Click to expand...
I don't pay for my medication but I pay for my test strips and meter etc. I've been testing before and after meals for at least five years and I have a pretty good idea of what to avoid. Anything with more than 5g of carbohydrate per 100g of product didn't make it into my trolley. I managed to get my hba1c down from 143 to 53 but I never quite got it into the normal range.
Over the past nine months or so my blood sugar levels have risen markedly and have not come back down.
Practice nurse told me off for having cream, it's practically 100% sugar according to her. She also told me that my hba1c has increased to 70+ because I am so stressed out by pricking my fingers. She also recommended the "eat well" way of eating.
Anyway I was referred to a hospital clinic and the doctor wants to prescribe SGLT2 medication. I was concerned that he did not know that I had had a cyst on my pancreas as a child and also that I had had a C peptide test in 2021 which showed that my insulin production was very high. This doctor said that my pancreas would no longer be producing much insulin and said he didn't need to test it. I told my GP that I was worried and he has agreed that I should have the C peptide test.
I think that my GP is really good.
 
Swiggy said:
I don't pay for my medication but I pay for my test strips and meter etc. I've been testing before and after meals for at least five years and I have a pretty good idea of what to avoid. Anything with more than 5g of carbohydrate per 100g of product didn't make it into my trolley. I managed to get my hba1c down from 143 to 53 but I never quite got it into the normal range.
Over the past nine months or so my blood sugar levels have risen markedly and have not come back down.
Practice nurse told me off for having cream, it's practically 100% sugar according to her. She also told me that my hba1c has increased to 70+ because I am so stressed out by pricking my fingers. She also recommended the "eat well" way of eating.
Anyway I was referred to a hospital clinic and the doctor wants to prescribe SGLT2 medication. I was concerned that he did not know that I had had a cyst on my pancreas as a child and also that I had had a C peptide test in 2021 which showed that my insulin production was very high. This doctor said that my pancreas would no longer be producing much insulin and said he didn't need to test it. I told my GP that I was worried and he has agreed that I should have the C peptide test.
I think that my GP is really good.
Click to expand...
I too fund my own strips etc being a T2 diet only, thanks for sharing your story :) My question was directed to @rubyparkfj really as they seem to think we have to pay for everything in the UK which isn’t the case. I hope you get the answers you need now that your GP has agreed to the tests, there are some good ones out there - mine included :)
 
lovinglife said:
I too fund my own strips etc being a T2 diet only, thanks for sharing your story :) My question was directed to @rubyparkfj really as they seem to think we have to pay for everything in the UK which isn’t the case. I hope you get the answers you need now that your GP has agreed to the tests, there are some good ones out there - mine included :)
Click to expand...
Oh Loving Life, I misunderstood. I don't mind paying for my strips and things because I like feeling more in control of how things are going. I'm glad you have a good GP too, it makes such a difference.
 
For the record if I get to the point medication is being recommended I’d like to know what my insulin is doing before making choices which is most appropriate so I hope if I get there my gp is as helpful as yours
 
HSSS said:
For the record if I get to the point medication is being recommended I’d like to know what my insulin is doing before making choices which is most appropriate so I hope if I get there my gp is as helpful as yours
Click to expand...
Thank you
 
I had my c peptide test and I have now been waiting for more than a month for my results. My GP has had the results of my full blood count which they say is fine but I have no idea what that is. The receptionist said that I will just have to wait for my results to come through and confirmed that they did request "everything" including c peptide.
I'm fed up.
On a happier note my glucose levels have been coming down steadily, possibly because of the increased Metformin, but I'm very pleased.
 
Swiggy said:
I had my c peptide test and I have now been waiting for more than a month for my results. My GP has had the results of my full blood count which they say is fine but I have no idea what that is. The receptionist said that I will just have to wait for my results to come through and confirmed that they did request "everything" including c peptide.
I'm fed up.
On a happier note my glucose levels have been coming down steadily, possibly because of the increased Metformin, but I'm very pleased.
Click to expand...

I had a C-peptide blood test privately, and then a C-peptide urine test by my consultant. The blood test showed as low c-peptide levels, the uring test showed normal levels, but that's because I have reactive hypoglycaemia during exertion, and very little insulin production when sedentiary. It would pay to get a trial on the Libre2 sensors to see what your patterns are like over an extended period. Insulin resistance isn't just caused by obesity. Stress, viral/bacterial infection and also hormones can cause it,
 
I always arrange to have a copy of any test results. It's a legal right, though I have never had to say this (catch more flies with honey than vinegar). I simply contact them and ask when it would be convenient for me to collect my print-out (can be sent digitally if preferred) which leaves no room for challenge or refusal.
 
Hi, I thought I'd update here and ask for a bit of advice.
I had blood drawn for C-peptide test in July but I never got the results back. I asked for them but was just told that my full blood count was acceptable.
My GP agreed that I could have another C-peptide test and I had it done on Wednesday. That result isn't back yet but my hba1c has reduced from 82 in March to 62 on Wednesday. I'm delighted by that and I look forward to the rest of my results.
My question is about my code free meter and the my sugar app. I test before and two hours after everything I eat and my estimated hbA1c on the app was 94 but the test I had on Wednesday is 62. In March it estimated 140 so both the estimated result and the actual result has come down.
Should I continue to test before and after each meal and hopefully continue to see my estimated hbA1c come down and not worry about the accuracy or should I buy a new meter.
Sorry for the long post . X
 
Swiggy said:
Hi, I thought I'd update here and ask for a bit of advice.
I had blood drawn for C-peptide test in July but I never got the results back. I asked for them but was just told that my full blood count was acceptable.
My GP agreed that I could have another C-peptide test and I had it done on Wednesday. That result isn't back yet but my hba1c has reduced from 82 in March to 62 on Wednesday. I'm delighted by that and I look forward to the rest of my results.
My question is about my code free meter and the my sugar app. I test before and two hours after everything I eat and my estimated hbA1c on the app was 94 but the test I had on Wednesday is 62. In March it estimated 140 so both the estimated result and the actual result has come down.
Should I continue to test before and after each meal and hopefully continue to see my estimated hbA1c come down and not worry about the accuracy or should I buy a new meter.
Sorry for the long post . X
Click to expand...
I'd push to get those C-Pep results.

In your shoes I'd continue to test. The test is most important for working out how well you're dealing with various foods, not as a "predictor" - it's a really bad predictor.

There's a huge number of posts on these forums about the near impossibility of predicting HbA1c from fingerprick tests. They test different things (blood glucose versus glycated red blood cells) in different ways, and both can be inaccurate - for example the fingerprick has up to 15% allowable inaccuracy for 95% of tests (5% can be completely off the wall).

A new meter will work to the same standards as the old one. I'm still on my original (free) Gluco RxQ, which is really basic but the strips are cheap and it's been a constant over the last five years.
 
Swiggy said:
Hi, I thought I'd update here and ask for a bit of advice.
I had blood drawn for C-peptide test in July but I never got the results back. I asked for them but was just told that my full blood count was acceptable.
My GP agreed that I could have another C-peptide test and I had it done on Wednesday. That result isn't back yet but my hba1c has reduced from 82 in March to 62 on Wednesday. I'm delighted by that and I look forward to the rest of my results.
My question is about my code free meter and the my sugar app. I test before and two hours after everything I eat and my estimated hbA1c on the app was 94 but the test I had on Wednesday is 62. In March it estimated 140 so both the estimated result and the actual result has come down.
Should I continue to test before and after each meal and hopefully continue to see my estimated hbA1c come down and not worry about the accuracy or should I buy a new meter.
Sorry for the long post . X
Click to expand...
You have the right to the numerical results (with units and reference range) of your tests. I’d ask for them from both tests. Great news on the hba1c going in the right direction though.

The accuracy of the app predictions is based upon how often you test and how good a representative sample that is. If you always test at your lowest points and miss highs it will predict a result too low. If you test only at the high points and miss the more stable lower ones it’ll predict too high. With finger prick tests there is a distinct risk GIGO applies (garbage in garbage out) when it comes to estimating hba1c. So based on that I see no obvious reason to buy a new meter.

Do you know how many carbs you eat a day/meal? What sort of difference are you seeing between pre and post meal readings? At an hba1c of 64 it suggests that carbs in V ability to cope with them for whatever reason hasn’t been reached. Fundamentally either you don’t have enough insulin to cope with that level of carbs due to low production or you are too insulin resistant for your adequate/ample insulin to overcome the resistance at that level. It makes a difference which, in order to choose the available paths forward for meal and medication choices. It’s also worth noting that eating very low carb and taking sglt2 medication is contraindicated, due to the risk of euglycemic DKA. If they are recommended again please make the prescriber aware you are already eating low carb /keto (whatever is appropriate).
 
Back
Top