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Thyroid UK
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Help please with Vit D test results.

A friend has just got print outs of all her test results and is confused about her Vit D. The most recent shows VIT D total serum 22nmol/L (50-120) which is clearly deficient by anybody's standards.

However, she's noticed a test from 2011 which shows R PLASMA 25-OD VITD 42.8 nmol/L (20-110) - apparently just within range, but what is the difference between these 2 tests please?

She has now been put on an 1,800 iu supplement, but I think this is far too little. What does anyone else think?

13 Replies

I think it's low too. My vitD was <10 in Nov and I was put on 40,000iu daily x 7days and am on maintenance 2,000iu daily for 3 months or until my imminent blood test shows I'm sufficient. If your friend can't persuade her GP to raise the dose she could buy sublingual tablets or spray on Amazon (please use the TUK pinned affiliate link).


If you take a look at the British National Formulary (the book that gives dosages of standard drugs a doctor can prescribe), it seems your friend has to convince her doctor that she is suffering from...

"Vitamin D deficiency caused by intestinal malabsorption or chronic liver disease usually requires vitamin D in pharmacological doses, such as ergocalciferol tablets up to 1 mg (40 000 units) daily; the hypocalcaemia of hypoparathyroidism often requires doses of up to 2.5 mg (100 000 units) daily in order to achieve normocalcaemia."

Your friend is being treated at levels considered suitable for "simple deficiency".


I decided to supplement my own barely "adequate" vitamin D level with 1000iU Vitamin D3 per day, and my level dropped quite drastically. So now I supplement with 6000iU per day.

It is important to supplement with vitamin D3 (colecalciferol), by the way, NOT vitamin D2 (calciferol) because that doesn't work nearly as well. If the supplement doesn't specify what it is, don't buy it.


Many thanks for posting Sue, and thanks for response human bean - my son has just received his endo letter saying endocrinologically he is "fine" - ferritin is normal and Vit D is 25 ( no reference range given, so he can take 1000iu per day, also advising a coeliac biopsy test.

Seems there's a huge range of Vit D advised meds - much to learn.


Many thanks all for the helpful replies, confirming what I suspected. Will encourage her to give her GP a rocket.


there's a good info package you can download from vitamin d council, I've put the link below for you, or just take look at their site,, our docs still mostly look at bone protection when it comes to vitamin.d ranges ,, a more up to date range shows over 75 as sufficient,, I'm inclined to agree that 1800 a day isn't enough,,especially in winter. but it's good starting point and sometimes we have to start off bit lower and work up,,I know I had to cos of dodgy guts . it took while to get my levels info range . there's some good info out there,, plus worth you doing a search on here for other vitamin d posts,, regards.... Ian


Hi The first test is considered more exact, different. However, that was too long ago anyway. You need a calcium test for corrected calcium as if it is over range not safe to take D ( a hormone )if calcium bellow range you need both, NICE D takes about 3 months to work, then retest both. For safety D should be only increased slowly on the results of both. Really it should be under an Endo too When both right, then 6 monthly checks.

Best wishes,





Here are some useful websites for now - my vitamin d was practically non existent - so was on high dose - I now take 5,000 iu in the winter - right or wrong - but I notice the difference within myself with a lot of things (main one being pmt) - apart from getting thyroid meds right of course.


Many thanks everyone for the useful links and suggestions




grassrootshealth.net/ This a useful Canadian website - looks old fashioned but good information. Good table indicating dose to take based on results. Please note the different measurements - so make sure you have the right one ! :-)


Thanks Marz - that's helpful.


Have a look at the booklet linked from here:




Thank you Rod.


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