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 eve

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.