Symptoms of low Vitamin D in your body are depression, weakness, fatigue, pain, dizziness, Mood Changes, Muscle Cramps, Muscle Aches, Muscle Weakness, Bone Pain and even stomach cramps.
If you're getting tired often, weak, have dizziness, depression etc then you may be low on Vitamin D.
You should see a doctor to get tested for low Vitamin D.
Vitamin D is essential to help keep you healthy and prevent viruses such as the flu, cold virus etc and having enough Vitamin D as well as Vitamin C helps boost your bodies immune system.
You can increase your Vitamin D intake by taking Vitamin D supplements or eat foods that contain Vitamin D and consume healthy drinks that contain Vitamin D as well.
Both Vitamin D and Vitamin C are healthy for you and required to stay healthy.
Also getting enough sunlight helps boost your immune system and keeps you healthy.