My vitamin D level is 14

I recently took a blood test to measure my vitamin D and Vitamin B12. My vit D was 14 and B12 was 450. I wanted to ask if I can take Vitamin D 60k supplements twice a week. Is it safe to take them twice a week if taken for a few weeks? what could go wrong? how long it could take for my vitamin D level to reach 50 if I take it once a week?