Hi , Iminabubble ,
Actually you have not been on a 'highish' dose You have been on a lowish dose, let me explain.
In sunshine ( our normal source of Vitamin D) , our skin will make about 10,000 to 20,000 IU per day . It takes about 20 mins or so , for any patch of skin to saturate, so, IF you sunbathe , on both sides , in strong sunlight your body can make 20,000 IU. More than say 1/2 an hour is excessive , in strong sun , on any particular bit of skin. IF you are white skinned. There is no need to burn , or become red , etc.
Our second source of Vitamin D , is food , absorbed via our intestines , it is , or likely to be about 20 % of our provision, depending upon our diet. Vegetarians will likely have a lot less from food , it is not present in fruit or veg. and only tiny amounts in eggs. ( there is some in wild oily fish, but farmed fish is much depleted , only a 1/4 of the level )
Supplementation , via capsules or tablets or spray can give us more. Many people with absorption problems will use a spray because it goes directly into the bloodstream and bypasses the digestive system.
You have said that you do have digestive problems , and low B12 does suggest Pernicious Anaemia , which is considered to be an autoimmune problem of the gut. or possibly you have a fat digestion ( bile) problem, hindering reuse of the B12 that is already in your system. Both of these problems may result in reduced Vit D absorption through the gut.
A healthy 75 kg adult can expect their blood level of Vitamin D to be a raised by about 25 nmol/L for every 1000 IU of supplementation per day over the long term. There is a great deal of variability. SOME people will exceed that , some will have a much lower response.
It seems that you have a response at the lower end , and may need to take more than average to achieve more healthy blood levels. The blood level should be in the region of 120 -140 or more. That is a normal blood level. It has been for millions of years. It is only recently that here in the UK , we have much less. If you were living an outdoor , old fashioned lifestyle , you level would rise to those levels. Indeed , they do ... we have measured it , in Lifeguards etc.
You will help yourself if you get there. To do that you have to take more supplementation , BUT , you do have to make sure that your blood level responds as you expect. You could take gel capsules , lets say 5000 IU per day , or you could take an oral spray say 2 puffs of 3000 IU per day. In 3 months your blood level will stabilise , with those constant doses. Don't stop supplementing unless your blood level is too high . Which looks very unlikely , from your description. Too high would be over 200 nmol/L . Just reduce your dose a bit. OR increase it a bit , according to your result , then wait 3 months , with your new constant daily dose, for your level to stabilise , then measure again.!
In order to measure your level , you could ask your doctor , but often they are reluctant to remeasure ... or, you could get a test from this NHS lab, a bloodspot , sent to the lab in Sandwell , City hospital Dudley Road, Birmingham. You will get an email with the result within a week. <a class="break-all" href="http://www.vitamindtest.org.uk/" rel="nofollow" target="_blank">www.vitamindtest.org.uk/</a> unfortunately they do charge £28 if the test is not doctor ordered.
I have posted quite a bit here on mumsnet about this problem ( low vitamin D ) .
Here is a good thread to have a look at , many people with their experiences , how they supplemented , how it helped. Quite a long read , but lots of information. www.mumsnet.com/Talk/general_health/2421492-Vitimin-D-can-it-have-this-effect!
Or search my nickname , here on mumsnet, or on Google.
Best of luck ,
and if you need any more information , get back to me .
BTBH
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