Some people don't convert sunshine to D3 well. That's why it's recommended everyone get tested, even if you're outdoors a lot.

Here are a couple of studies showing how at the same latitude there is a difference between the vitamin D levels achieved by people living in the country and in the town.
The effects of air pollution on vitamin D status in healthy women

Urban Tropospheric Ozone Increases the Prevalence of Vitamin D Deficiency

However those examples are from Belgium and Iran.

In the US it's a bit more complicated because agriculture has become so industrialized.

Growth of Continental-Scale Metro-Agro-Plexes,Regional Ozone Pollution, and World Food Production Three regions of the northern mid-latitudes, the continental-scale metro-agro-plexes presently dominate global industrial and agricultural productivity. Although these regions cover only 23 percent of the Earth's continents. they account for most of the world's commercial energy consumption, fertilizer use, food-crop production, and food exports
They also account for more than half of the world's atmospheric nitrogen oxide (NOJ emissions and, as a result, are prone to ground-level ozone pollution during the summer months. On the basis of a global simulation of atmospheric reactive nitrogen compounds, it is estimated that about 10 to 35% of the world's grain production may occur in parts of these regions where ozone pollution may reduce crop yields. Exposure to yield-reducing ozone pollution may triple by 2025 if rising anthropogenic NOx emissions are not abated.

More recent research shows Ozone concentrations [O3] in the industrialized countries of the Northern Hemisphere have been rising at between 1 and 2 per cent per year (Chameides et al. 1994). The surface [O3] has now reached a global mean of approximately 50 ppb (8 h summer seasonal average; Fiscus et al. 2005). Nearly a quarter of the Earth's surface is at risk of experiencing concentrations in excess of 60 ppb during mid-summer.

So it's possible that even living in the country in the US could be as bad for ozone as living in the city.

You've got to have UVB to convert the cholesterol in your skin into vitamin D.
Insufficient uvb because of higher ozone levels means less Vitamin d.

I don't have to explain how lowering your cholesterol levels with statins inevitably prematurely ages your skin and decreases the ability of skin to make vitamin D. Saying low cholesterol = low vitamin D potential is simply stating the obvious.

Whatever method you are using to ensure you have a natural vitamin D status above 50ng/ml it's important to check with a 25(OH)D test so be certain what you are doing is sufficient.

Dr Davis put a link to DIRECT LABS Vitamin D, 25-Hydroxy-October Test of the Month $39 Which sounds like a bargain to me.

That's a great price! When I first had it done in March it was $90. This last test (same lab) was $70. I should order a couple at this price!

Apparently you can only order 1. Is this a reputable lab?

The Vitamin D3 gel capsules that I bought today at 5000 iu's were $22.00!! That is for 150 capsules, but man!!

Geezum crow! I don't get the gelcaps, but I do always take them with plenty of fat. You might want to consider that next time.

I doubt Dr Davis would link to it if it were in any way dodgy.

Country Life, Vitamin D3, 5,000 IU, 200 Softgels SRP: $17.99 Our price: $10.20 (£6.69)
As it is sensible to take one of these every day from now till you die you will save a lot of money over the course of you life by shopping more sensibly.

While Iherb is probably cheapest for the UK (postage $4)
USA delivery $2 + 10.20= $12.20 for 200 x 5000iu
Code ~~~~~~ SAVES $5 off your first IHERB order.

Vitacost do the same for $8.10 + $4.99 shipping = $13.09 but they have a 10% discount this month so may work out cheaper

I prefer these because they are in MCT oil and that has a long shelf life and Medium Chain Triglyceride oil has other benefits although because the capsules are so tiny and the amount of oil used as carrier to small those benefits are somewhat more theoretical than real.
However it's certainly not a good idea to add to your omega 6 burden so olive oil or fish oil are next best and those in soy or sunflower best avoided.

Hutch (mind if I call you Hutch?), you're the BEST!!!

In 150 days when these capsuels are gone, I am going to order from vitacost. Thank you so much!! You really are the best!

Yes, it's reputable. I get the other tests I need from this lab.

I went ahead and ordered a test from them the other day for $39. Unfortunately, you could only order one. Hmmmm. One at a time, that is. Maybe I should place another couple of orders......

Will they let you fill them 3-6 months down the road?

Just want to bookmark this thread. That lab looks promising and I have some tests coming up in November.
D3 is one of them...

Nancy,
You'll have to check with them because I'm not sure I remember correctly. I think the lab slip is good for three months but I'm not positive.

That $39 price is their October special so I would order at least one more. Also, check with them if they will replace a lab slip if it goes out of date...Cancellations/refunds are good for up to six months so they might.