I was diagnosed with Chronic Fatigue Syndrome 1.5 years ago. I looked high and low for which supplements to take to help with energy. I was already taking a good probiotic and cucurmin and then added in the Vitamin D. It made a quite a difference in how I was feeling. My energy levels went up, and that just made me feel better. I love that this is made in the UK (I prefer brands that are manufacturered in the UK as they have standards they have to meet for quality). If you're looking for a high quality Vitamin D, this is a great option. Highly recommend.