Back in August I mentioned I was doing an experiment to see what effect taking Vitamin D supplements would have on my serum Vitamin D levels.

The test was over 8 weeks and I now have the results.

Process followed

The paper Immunologic Effects of Vitamin D on Human Health and Disease states “To maintain these blood levels with minimal sunlight exposure, a person would require ingestion of 4000–6000 IUs of vitamin D daily, which would maintain serum vitamin D levels in the range of 20–40 ng/mL (50–100 nmol/L) and serum 25(OH)D levels in the range of 40–60 ng/mL (50–100 nmol/L)”.

From that I decided to take 5000 IUs per day using readily available 1000 IU (25ug) tablets from a reputable source.

There has been some suggestion that tablets are best taken with food - which may help with the absorption of a fat soluble vitamin, and that taking Vitamin D late in the day may disturb sleep.

I settled on taking the tablets three times a day with meals. Two at breakfast, two at lunch and one at dinner.

The paper also quoted dosage details from the Endocrine Society suggesting an intervention like this should run for 8 weeks for adults (> 18 years).

My compliance over the 8 weeks has been pretty good. I’ve only forgotten a few times. Following good practice I haven’t topped up when I’ve missed a dose.

I haven’t noticed any adverse effects from taking the tablets over the period. In terms of positive effects, I appear to have avoided catching the fairly severe “back to school cold” that both my children went down with in the first week of going back to secondary school, but I’ve noticed little other change.

Activity levels have reduced a little - down to an average of 3500 steps per day thanks to the deteriorating weather and darker nights.


The updated results from the lab are:

Total Vitamin D : 88.1 nmol/L

which is an increase of 55.2 nmol/L over last time and in the allegedly useful range above 75 nmol/L

Follow up

From now on I’ll be switching to the maintenance dose of 2000 IU per day recommended in the paper and I’ll run that until next year before testing again to see if that is sufficient to maintain Vitamin D levels over the winter period.