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Insulin testing - which tests on the NHS?

LittleGreyCat

Well-Known Member
Retired Moderator
Messages
4,386
Location
Suffolk, UK
Type of diabetes
Type 2
Treatment type
Tablets (oral)
Dislikes
Diet drinks - the artificial sweeteners taste vile.
Having to forswear foods I have loved all my life.
Trying to find low carb meals when eating out.
I'm confused as usual.

There have been a number of threads about testing for insulin production and insulin resistance, many of which say that the tests are not available on the NHS and you have to arrange for blood to be drawn at your surgery then send it off to a laboratory.

For example https://www.medichecks.com/diabetes-tests/insulin-resistance-test which claims to run 3 tests (but doesn't seem to say what they are in detail).

However there is also much mention of the c-peptide test. http://www.diabetes.co.uk/c-peptide-test.html.
The description says:
"
What is C-peptide?
C-peptide is released at the same time as insulin.

For each molecule of insulin produced there is a molecule of c-peptide. C-peptide does not itself influence blood sugar.

C-peptide is a useful marker of insulin production because c-peptide tends to remain in the blood longer than insulin.
"
As I understand it, a c-peptide test (along with GAD) is the standard method of distinguishing between T1 and T2 on or after diagnosis. As such it must surely be a standard test available under the NHS.
The description looks pretty good - an accurate and longer term marker for the level on insulin production.

So what are the tests for insulin production and insulin resistance which are not a c-peptide test and are not available under the NHS? How are they better than c-peptide?

Supplementary:
I am on LCHF. I read on this forum that if you are on long term LCHF and in nutritional ketosis your insulin production drops, so much so that if you need an OGTT you should increase your carbohydrates for a few days before hand, to kick start your beta cells to produce more insulin so that you don't get a false reading when you take the OGTT.

Given that, would a c-peptide test for someone on LCHF show a misleadingly low reading? Should you increase the carbohydrates for a couple of days before the test in the same way you do for the OGTT?

Or doesn't it matter? My concern is to establish if I am insulin resistant. Would someone insulin resistant automatically be running high c-peptide levels?
 
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As far as I am aware, the c-peptide test can be performed by the NHS and is used, as you say, to help decide if someone might be T1. I have no idea if the NHS will pay for such a test to someone that clearly isn't a T1. You could always ask.

The "rules" for the OGTT say you need to eat at least 150g carbs a day for 3 days prior to the test to give your pancreas chance to wake up as it is no longer used to producing enough insulin for a sudden shot of pure glucose.

The fasting insulin test is not done on the NHS. A few members on here have used the Medicheck test and have recommended it. The only problem could be persuading your surgery to allow the blood draw, so maybe worth waiting until your next lot of blood tests and ask for it to be added. Or you could just ask your nurse or use one of the blood clinics in your area that on the list the Medichecks website gives. It is the insulin test that you need. (£39)

I did the Rapilose OGTT at home but didn't carb up beforehand. I found it useful. A few others have also done it and found it useful.
 
The fasting insulin test was the one I had done by Medichecks.
If you are Type 1 the result should be close to zero (producing no insulin)
If you have insulin resistance you will producing lots (greater than about 8 I believe although some say greater than 5 )
So it is a reasonable test to show the state of play in your insulin production. My results from the first time were 3.41 miU/l and the second one 7.85 miU/l so I'm kind of ok.. their reference range is 2.60 to 24.90 as "normal'. Anything over that would imply insulin over production.
 
A normal fasting insulin test will include the insulin someone is injecting. A c-peptide test shows how much insulin someone is making themselfs, by measuring one of the byproducts of the body making insulin.

The c-peptide test was first developed to it could be used along side a normal insulin test to see if someone had been killed by injecting insulin into them.
 

So far as I know @LittleGreyCat is only on metformin.. at least that what the signature says..
 
Hi C-peptide is used on the NHS but it does cost and many surgeries will avoid it or don't know about it. I got Medi-checks to do mine privately. My result was near to the bottom of the 'range' as I suspected.
 
Daibell said:
Hi C-peptide is used on the NHS but it does cost and many surgeries will avoid it or don't know about it. I got Medi-checks to do mine privately. My result was near to the bottom of the 'range' as I suspected.
Click to expand...

Which are the tests that Medichecks does?
I can see an insulin test for £39 (one test) and an insulin resistance test (3 tests).
I haven't tracked down what all the tests are in the £49 one.
Ah. Obviously not c-peptide because that is £99.
Looks as though there are two things measured - blood glucose and insulin - and then an insulin resistance index is calculated. So it looks as though this is not a fasting test, although there is no guidance about how soon after a meal this should be taken.
The insulin test also doesn't say that it a fasting test so possibly it is only testing for your insulin to be between a low and high range which covers from fasting to just having eaten. Or that the ratio is the important thing.

So - anyone who has had the insulin test (@bulkbiker) did the instructions which came with the test specify that it should be fasting? The web site doesn't seem to mention fasting for either test.
 

I just had the insulin test and fasted beforehand.. hence it was a fasted insulin test. Then again I fast every morning anyway so I just avoided tea or coffee on those day. The first one I had the blood taken at 11.45 the second one at 8.15 Looks like the Insulin resistance test just adds in a blood glucose test as well and then works out your Insulin resistance from that which someone put a link up to a calculator.. (will have to search around for that). So you can take your own BG reading at the time they do the blood draw for the insulin test and work out your insulin resistance for yourself and save £10.00
 
@LittleGreyCat

I think an insulin test is usually done as a fasting one because of the interaction between our livers and our pancreases. When fasting the liver is triggered to dump glucose, and then the pancreas is triggered to secrete insulin to combat this glucose and push it away in the cells. When there is insulin resistance, the secreted insulin can't do its job, so the pancreas continues to produce more insulin until enough has been secreted to clear the liver dump. So .... in a fasting state, if our serum insulin is low, it will because it has done its job and the pancreas is no longer having to keep secreting. In other words - no insulin resistance.
 

Interesting. This does imply that the test should be done the very first thing in the morning if the main aim is to measure the level of insulin production versus the level of glucose secreted by the liver.

It also implies (I think) that if you have a normal BG after fasting over night then by the time you are tested, as your BG is normal your insulin is likely to be normal as well - although it is possible you could have normal BG but still high insulin because you are resistant and had to secrete more to bring your BG level down.

I will contact Medichecks to see what they advise.

@bulkbiker a finger prick test is notoriously inaccurate; certainly compared to a laboratory. So an extra £10 for a more exact test using the same venous sample seems worth the extra £10.
[Noting that I accidentally tested my BG instead of my ketones today with my new CareSens Dual using the same drop of blood (quite big) as I tested a moment later with my usual Freestyle Freedom Lite. CD 5.1, FFL 5.9, So I think I would rather use laboratory calibrated professional test equipment.]
 
£10.00 maybe a small price to pay, if you use it as a way to check how well your meter is working, by taking your own reading of BG at the same time as the blood sample. (Also, your own meter is not testing the same blood, so the BG reading it gives can be as much as 15 minutes "out of date".)

LittleGreyCat said:
It also implies (I think) that if you have a normal BG after fasting overnight then by the time you are tested, as your BG is normal your insulin is likely to be normal as well.
Click to expand...

Not true, most of us would have had high insulin but normal BG for 20 or more years before our BG went out of control. The high insulin is also responsible for most strokes and heart attack due to the damage the high insulin does to the body over many years.

Hence fasting insulin should be a standard NHS test for everyone so people can be told their bodies hate carbs long before they get Type2, hence avoiding getting Type2.
 
Nice prompt response:
"Thank you for your enquiry.
Please see the special requirements below for these tests:
Fast 10 - 14 hrs prior to sample being taken.
Preferably have sample drawn in morning.
Do Not consume alcohol 24 hrs before test.
DO NOT cease prescribed medication without consulting your Doctor.
I hope you find this information helpful, if you have any further questions please come back to me and I will be happy to help you."
 
It would be useful for many of us to know more about the various tests. I went for the c-peptide as I was convinced I had low insulin and as I was tick thin my insulin resistance should have been fairly low. Others who perhaps have some excess weight or just suspect insulin resistance may prefer the IR test? The c-peptide guides you into the right action ref meds and diagnosis whereas the IR may relate more to the cause of your diabetes and the dietary action; doing both would be even more useful.
 
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