Not GP, but my level was 8 nmol/L in the middle of summer. No medical explanation could be found for why I was so deficient, and I get at least 1hr sunlight every day during my daily cycle commute (UK). Symptoms were depression, tiredness and disturbed thinking.

I was prescribed vitamin D3 10,000 IU/day.

This is extremely low. And what about now, after the 10,000 IU/day supplementation?

I was around 15 nmol/L (I think). 20 was the minimum. I checked a few months after starting my new regime, and it had gone up to about 50. I then tried backing down to 4000 IU a day and it fell back to around 40, so I went back to 10000, and I haven't checked since then, but I do know my antibody counts are down.