Been wanting to write about vitamin D for ages, and many thanks for all your posts/advice on this and related subjects, so here is now my current view/understanding on it so far.
Vitamin-D seems to be one of the key things we can take action on ourselves, to perhaps slow down the CLL growth rate.
As I understand, your liver converts vitamin D to its “bio-active” form 25(OH)D and that is what you test for.
Wiki seems to give a fairly good write-up and more detail on that:
en.wikipedia.org/wiki/Vitam...
… but I've always been a bit confused and thought that ideally you need some sun-exposure as well as the dietary intake (perhaps the trick is though, getting the diet correct, and I note the point that we were designed to acquire the vitamin from sunlight, so eating oily fish etc. (or supplements) is perhaps a workaround, but a safer one)
For the supplements, at the moment I do a morning multivitamin (5ug 100% RDA) and at the end of the day x1 Cod-liver oil pill 3.37ug 68%RDA).
Eat oily fish about 2->3 times a week (used to eat cold smoked salmon, but gave that up after deciding excess of smoked stuff probably not a good move)
Aside: only learning to pop pills again after having trouble with swollen tonsils since 2003 (finally had them out start of this year, donated them to medical research 
and yes they did contain some CLL. Moral get them removed when the antibiotics don't work (10 years ago) . . .
If I looked at the two things I might have done wrong in my life (apart from being a familial case of CLL, which isn't understood), lack of sunlight in the past 10 years would be one, and lack of sleep the other (I note the very interesting BBC2 program Thursday the 10th Oct “Trust me I'm a Doctor” by Michael Mosley about loss of sleep this week; you have already posted on. Would be interesting to get Michael to do a program on CLL ? And I think the general public all around the planet needs to have a serious think about all the great new cancer drugs being invented, even in the most wealthy countries. India seems to be the one with clear thinking . . .)
Another observation, is the few times (not many) in the last 10-20 years I have stopped getting outside and doing the garden, the general health seems to have suffered – and I've never totally got my head round exactly why – could be several different reasons, but perhaps the sun-light is more Important than I've thought before.
Anyhow, just got my first vitamin D / 25(OH) D test result in September, and scored 100 (not had the official report yet), and sorry I'm a dummy, didn't ask the units, in my excitement.
I was told the acceptable range (in UK units) was 80 to 150, my result was ok and next test would be a winter one in 6 months time. That is ok, but with a UK winter I'm sure in my mind that is not going to be a good result . . .
Following suggests UK units will be in nmole/L
vitamindcouncil.org/about-v...
. . . and a conversion factor of divide by 2.5 to get ng/mL
Sometime we will have to have a humerous post on moles (not the cute brown furry kind), have a look at:
en.wikipedia.org/wiki/Mole_...
and note the sentence “one mole of a substance, expressed in grams, is exactly equal to the substance's mean molecular mass”
So a mole is a number of molecules (the Avagadro constant) and the conversion factor will then depend on the mass of the molecule.
Put the physical chemistry to one side for another day, and do the sums:
100 nmole/L divide by 2.5 = 40 ng/mL
Taking the Mayo clinic as an example (scroll down to the table and press the “enlarge” button):
mayoclinic.org/medicalprofs...
They quote units of ng/mL and say 26->80 ng/mL is OK and above 80 risks toxicity.
So I could double my reading and still be in range.
Without any test results, I note the UK NHS suggest maximum of 25ug vitamin D per day in the following, which is way over what I'm doing, so I conclude testing is essential for those of us with CLL that want/need to get near to the right target:
nhs.uk/Conditions/vitamins-...
Beware the above reference seems to have a contradictory bit at the end about sun exposure ( I think in the UK the issue is most people get to see so little sun in the year, that on the two days it does shine, when they are not at work etc. etc. they end up with gross over-exposure / sun-burn / health risk, or we go abroad to achieve the same all over red finish)
I note the previous HU articles on sun exposure, so in the summer I always wear a wide (older style) Tilley hat (my dad did get minor skin cancer – not severe – on the side of his head, after suddenly starting sunbathing at the age of 60. Only now 25 years later I assume he was trying to top up his vitamin D levels to combat the CLL silly me.
The other thing I've had to do when gardening is wear an old linen shirt (I assume my thermostat is going wonky because I'm now rather thin, yet I overheat now at the slightest thought of exercise).
I note others here on HU/CLL going for long sleeves to avoid burning the arms which get over-exposed, but there I'm just too hot so have to rely on factor 30, and shove a bit on the top of the shoulders under the shirt, which will let through some light.
So questions are now:
1. How much to up the dose of the Cod-liver oil pils (I assume that will have to be best-guess until I get a winter test result. I'm thinking 2 more a day in my case with the above figures.)
2. Anything else I can do this winter (short of getting a job/project in Australia – I did manage that once a long time ago – happy days)
3. Any good write-ups to read
Ernie
P.S. As usual, please point out and correct my blunders above.
P.P.S. The picture above hopefully proves the sun did shine this year in the UK - never seen so many butterflies since I was a kid
Low vitamin d high serum ferritin 
CLL / Skin Cancer - getting it checked in the UK
Going on Medicare part D 
Medicare Part D question
