Hello ,
Vitamin D deficiency at your age is uncommon and might occur due to some GI ailments like malabsorption syndrome etc, if you are experiencing any symptoms like fatigue , tiredness , dysthymic or low endurance u can get ur general checkup done frm a MD med doctor, till then you can start Tab sunrise 60k once a week tablet as a supplement for your vitamin D levels for a total of 8 weeks and check your vitamin d leveles again.
Next Steps
Observe & consult in case of symptoms