My blood cells are 15 and my vitamin d is 6.60

Welcome, and thank you for trusting us 

Regarding your question
vitamin D level below 12 nG/mL considered as deficiency
for the blood cells if you please put the unit

what is the treatment of vitamin D deficiency

1. sun exposure daily between 10 -20 minutes
2. oral supplements (50000 International unit daily)
3. eating diet rich with vitamin D as fish and egg yolk and beef meat

what are the symptoms of vitamin D deficiency

1. bone pain
2. easily fractured after trauma
3. constipation
4. perioral numbness

how it is diagnosed

1. clinical exam
2. vitamin D level in the serum

I hope my answer was helpful, please let me know if you have any follow up questions. If you feel I've answered your question already, please rate my answer from top of the page. 
Your feedback helps to ensure only the best experts are available to help you.  You can also ask questions of our other specialists in the areas of nutrition, therapists, IT specialists, medical doctors, and many more..  Kind Regards