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Vitamin D test results: a bit of a mess

I had bloods done privately a couple of weeks ago and the result of the vitamin D test came back as 17nmol/l (<30 indicates deficiency). 'Holy moley!' I cried, 'I must get down the doctor's straight away and start treatment'. Duty GP, I thought unreasonably at the time, grudgingly accepted test result and prescribed Vit D3 1000u but insisted on me being tested again. This was 8 days after the original test.

New test results are 103nmol/l. How can that be possible, apart from lab error? I've not gone out in the sun more and didn't start the tablets until after the retest.

So now my doctor thinks I'm more nuts than she already did (although she is a fabulous GP and I wouldn't be alive without her).

Has anybody else had a similar experience?

14 Replies

Clearly it is not possible for both of those test results to be correct. However, who is to say the second NHS test isn't the inaccurate one?

I took a private test result to my GP for vitamin D and I did get the "are you crazy" look from the GP but he did treat the vitamin D on the basis of the result so I can't complain. I have my 'usual' GP but every now and then I have to see someone else and they invariably order tests which I'm pretty sure my usual GP thinks is a waste of time.

Anyway, what symptoms do you have?


Symptoms? Just the ones that overlap with iron deficiency (which I also had done privately at the same time and which tallies with the NHS retest); had them done as per recommendations of this site. I am inclined to think that the NHS one is probably correct based on the time of year and the fact that I am a redhead so should be a champion synthesiser of sunlight to vit D.

Based on the original low vit D test I got my calcium level tested too and that came back right at the bottom end of the normal range (like, slap-bang on: any lower would have been a deficiency). I would have thought this result would tally with the low vit D?


Are you sure the first test was measured in nmol/L or ng/L ? Just a thought :-)


Ooh, you're right. On checking, the first test was ng/ml, or 43 nmol/l. The lab report says a moderate deficiency is in the range of 10-30 ng/ml and that 30-100 is the preferred range. A quick google tells me that 17 ng/ml equates to about 42.5 nmol/l. That is quite low, isn't it? Could that explain the borderline hypocalcaemia?


My Vit D test came back as 62.4 mnol/L.

I saw my GP last week she said my Vitamin D is too low, should be 75


Try again Vit D came back as 62.4 nmol/L

My GP said should be above 70 to 75.


I'm still baffled about the discrepancy between the two tests, taken about a week apart! To go from 43 nmol/l to 103 nmol/l in a week is insane.


I would be as well, as your second test would you leaves you in the optimal range 75-200.

I would want to make sure which of these readings is correct.


But even if the original test results translate to 43 nmol/l, that's quite a difference to the 103 nmol/l result eight days later!


Hi If you used blue horizon , it is a better, different test than GP, more exact. Mine is only10 but I cannot take D as have over range calcium.Endo is the person to treat this as hormonal.



Did you use the finger-prick test or go to have blood drawn? Are the finger-prick tests reliable, do you know?


I use the finger prick if hard yup, either the Birmingham hospital of GP. Mostly I use the Blue Horizon or private hospital test, the only one my consultants think reliable.



Ooh, it would appear that there are two methods used to measure levels of vitamin D and they are not at all equal:

I bet that the French lab used the Diasorin Liaison method and not the mass spec.


They always rely on blood tests from the arm. Blood tests from the finger can be approximate why?

I am diabetic.

Me thinks the blood probably comes in packages as the constituents change. The one drop is produced that drop then dissolves in the body.

In much the same way the one drop

Comes out of the body and the content settles at different concentrations. Laying down and standing up changes the flow hence blood pressure.

The great volume taken by the surge

Gives a more accurate perhaps answer...

But if you take blood over a period of time the finger prick test might be more accurate? Compared to the larger volume as a one off test.

If your unstable diabetes they put you on a sampling machine.

The average accuracy of these tests is about 25% that's why you need to keep an eye on what's happening on previous tests and having the test at the same time of day.

Ideally it would be good if they would do it over 24 hours. With home testing we can do that.

But it does not mean the doctor knows enough. I did the stress test

I even ran up and down the stairs. Before I too the morning salver it was still low.

I showed this test to several consultants they said that your morning cortisol will below sometimes.

All it matters is..

The docs don't recognise the two types of adrenal stress..

They don't even as a whole know what DHEA is that's an endocrinologist. The one I saw at Leicester had not a clue... As I was talking his students chipped in and said What's DHEA? I said mine was low.

The endo had not a bloody clue it was not part of his remit.



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