These vitamins have been a true life-changer! I always half joked around about how I suffered from S.A.D. (self-diagnosed, yes), but in reality, I must have been severely D3 deficient. I have never had any levels tested to confirm a deficiency, I simply went on the recommendation of trusted friends (some of them nurses) to begin taking a supplement. Before I began taking these vitamins, I was a mess. I was suffering from vertigo (almost daily), severe anxiety (couldn't drive on the freeway), a foghorn type sound in my left ear (mostly at night, while laying in bed), and just generally feeling like crap. I began taking these vitamins and within about 1-1.5 weeks, I noticed a remarkable difference in how I felt. My energy level was much higher than it had previously been, and all of the other unpleasant symptoms seemed to fade away (no more highway driving anxiety!). To this day, I continue to take twice the recommended daily dosage, only because I've tried to lower to 5K per day, and noticed a negative difference. Also, I ran out of these at one point, and thought any old other D3 might suffice, but I was wrong. The same dosage of a different brand did not offer the benefits that these Garden of Life vitamins do. I'm so so thankful to have found these, and will continue to buy them (through Subscribe and Save, to ensure I do not run out...ever!)