Without vitamin D testing, doctors have to guess what a patient's levels might be, says Reinhold Vieth, a researcher at Toronto's Mount Sinai Hospital. (CBC)

Some governments are trying to limit the number of vitamin D tests ordered by doctors while provinces report higher demand for such testing over the past few years, CBC News has found.

Physicians order tests for levels of the sunshine vitamin for people with conditions such as osteoporosis, rickets, malabsorption syndromes and renal disease. Some family doctors are also ordering the test to screen healthy people for the level of vitamin D in their blood.

Numerous studies over the past five years have suggested vitamin D protects against different forms of cancer, staves off multiple sclerosis and fights infection.

In Ontario, demand has increased to more than 700,000 tests last year, from 29,000 in 2004. In emails to CBC News, British Columbia reported a 100 per cent increase in costs in one year, and in Alberta, Calgary has had a 400 per cent increase in tests in two years.

Ontario is considering paying for tests only when a doctor suspects a serious deficiency. The cost of the test ranges from $93 in B.C. to $32 in some Ontario labs.

At least five other provinces — British Columbia, Alberta, Saskatchewan, Manitoba, and Newfoundland and Labrador — have a similar restriction.

The change means doctors are losing the ability to screen their patients for vitamin D deficiency, said Dr. Linda Rapson, a general practitioner in Toronto.

"This is a big mistake," said Rapson, past-chair of the Ontario Medical Association's complementary medicine section. "This will be a lost opportunity to promote health and prevent disease. That's what it looks like to anyone who's been following the research literature."

Manitoba Health Minister Theresa Oswald said doctors in the province give priority to people with bone disease when ordering tests.

"If someone is appearing to be completely healthy but is very interested in their vitamin D status, what would likely happen is a doctor would advise that supplementation should begin, and that person would be put on a list to have that test at a later date," said Oswald.

Some patients take supplements and still don't absorb enough vitamin D, said Reinhold Vieth, a vitamin D researcher at Toronto's Mount Sinai Hospital.

"Without testing, the doctor is functioning blind," said Vieth. "You're guessing."

There is no consensus among doctors and researchers on optimal vitamin D levels, which Health Canada is reviewing. Physicians take into consideration factors such as latitude, skin colour, age over 50 and whether patients spend little time outdoors, which can influence how much vitamin D is absorbed.

'Key piece of my health picture'

When broadcaster and writer Gill Deacon of Toronto was diagnosed with breast cancer in April of 2009, she said guessing at her vitamin D levels wasn't an option. In addition to the recommended medical treatments of surgery and radiation, she looked at her diet and started monitoring her vitamin D levels.

"Getting that information on a regular annual basis and showing the progress or not and how much my supplements are working and what needs to be done, I mean, it's a key piece of my health picture," said Deacon.

Deacon said she'll continue to get the test, which is labour-intensive to perform, regardless of the cost.

Family physician Dr. Bowen Chan in Toronto is also concerned about vitamin D levels of some of his patients, such as postmenopausal women.

"Some people, they're coming from different countries, so they might have different levels or different exposures to sunlight, which is a natural source of vitamin D," said Chan. "So doing a blood test would actually help me determine if they actually need it or whether I need to adjust the dose."

Earlier this year, Statistics Canada reported that two-thirds of Canadians have blood levels of vitamin D falling below the level researchers now believe offers increased health benefits.

With files from The Canadian Press