Personally I am on 5000iu and apparently, this is the amount everyone should be on, not taking into account my health.
“Cannell references a relatively good study examining the vitamin D levels of people who get plenty of sun exposure, which was published by Luxwolda et al.  in the British Journal of Nutrition. The researchers discovered that healthy persons with traditional outdoor lifestyles, living around the African equator (the “cradle of mankind”), have average circulating vitamin D levels — ie, 25(OH)D — of 46 ng/mL (115 nmol/L).
Cannell remarks that most people do not have their blood tested regularly for vitamin D, so a recommended daily dose of supplemental vitamin D is needed that (a) is easy to obtain at pharmacies, (b) will get at least 97% of people above 30 ng/mL of 25(OH)D and most persons at 40-to-50 ng/mL, and (d) will not cause anyone to reach toxic levels. Besides those 4 goals, Cannell also takes into account body weight; since, apart from genetics, body weight is a significant determinant of vitamin D levels. The more a person weighs, the more vitamin D they need to take.
In support of this, Cannell describes a large study by Robert Heaney and colleagues that examined the relationship of body size and vitamin D status [see, Drincic et al. 2012]. These investigators found that, for a normal weight adult, 5,000 IU/day of total vitamin D input was needed to obtain a 25(OH)D level of 40 ng/mL. Cannell emphasizes that this pertains to an “average adult” and the final vitamin D level obtained by any dose also depends on baseline level, sun exposure, diet, and genetics.
More specifically, the researchers calculated from their data that a total input of 70-80 IU/day/kg-of-body-weight is needed to achieve 25(OH)D of 40 ng/mL. That works out to be about 35 IU/day/pound; so, a 100 pound woman would need 3,500 IU/day of total input, whereas a 300 pound man would need 10,500 IU/day. Note: this is total input from all sources, including sunlight, diet, and supplements.
Taking all of the above factors into account — and considering that most persons in modern society do not acquire much vitamin D from sunlight or diet — Cannell concludes that 5,000 IU/day of vitamin D supplementation is about right for the average adult.” (Pain-Topics)
Pain-topics has three references articles about vitamin D and pain:
- Vitamin D – A Neglected ‘Analgesic’ for Chronic Musculoskeletal Pain:
An Evidence-Based Review & Clinical Practice Guidance > Full Report [50-pages; PDF Here]
> Practitioner Briefing [7-pages; PDF Here]
- PPM Journal Article: Vitamin D for Chronic Pain [13-pages; PDF Here]
- Vitamin D: A Champion of Pain Relief — Patient Brochure [6-pages; PDF Here
- Vitamin D deficiencies have been associated with a variety of chronic pain conditions, such as back pain, osteoarthritis, fibromyalgia, inflammatory bowel disease, and others. In many cases, research has demonstrated the efficacy and safety of vitamin D3 supplementation in helping to alleviate pain and to improve functionality and quality of life.
- At the same time, much of the research has been of relatively poor quality and biased in one way or another. Larger-scale, randomized, controlled trials with higher vitamin D dosing and adequate follow-up times are still needed.
- there are inconsistencies in the quality and quantity of vitamin D content in over-the-counter supplements, and higher oral dosages (eg, 1,000 IU D3 tablets) are not available in some countries. Daily oral dosing of vitamin D is more consistent with “natural” intake than once-weekly or less frequent megadoses administered orally or via injection.
- The optimal dose of vitamin D3 supplementation and subsequent 25(OH)D levels in persons with pain have not been determined. While the 5,000 IU/day and ≥40 ng/mL 25(OH)D recommended above by Cannell may be adequate for healthy persons, this could be suboptimal in most cases for helping to ameliorate painful conditions. Research to date has not fully explored effects of more adequate dosing, long-term in pain management.
- Blood tests for vitamin D — ie, 25(OH)D serum-level assay — can be costly and inconsistent from one laboratory to another, but this test is the only way to know if supplementation frequency and amount are adequate for individual patients.
- Aside from the other factors that may ultimately influence 25(OH)D levels, possible interactions with medications — eg, antacids, anticonvulsants, corticosteroids, and others — may reduce the potency of vitamin D. Malabsorption syndromes and bariatric procedures have been associated with vitamin D insufficiency, as have alcohol consumption and tobacco smoking.
- Most persons get adequate calcium from their diet and do not need extra calcium in conjunction with vitamin D supplementation, unless specifically indicated.
So essentially everyone should be taking 5000 IU of vitamin D… but for chronic pain that might be different. It could be higher. And our medications may interfere with the absorption of it.So it is hard to say if 5000iu will be beneficial pay wise, but likely a good idea given everyone should be taking it anyway. Given I am Canadian and also avoid sunlight a good idea just for those facts.