At the time of writing this review I have been using creatine monohydrate for two weeks - with doses ranging from 10 grams to 20 grams. I have not directly taken any pure form of creatine, although I believe some pre-workouts I've consumed in the past have it in their blend.
I have been reading about taking large doses creatine and it's effect on brain function in the past, and I though what better way to prove it than to test it in my 9-5 job and see what happens And it did hit me hard. First two days took 15 grams immediately and on the third, I increased to 20 grams. The cognitive effect I did notice - noticeable are increased productivity while lacking sleep and better memory recall - but the negative side effects manifested physically. For about a week, I was goin to the toilet three to four times a day, with no other culprit than the pure creatine that my body was not accustomed to (I track everthing I eat with a food-logging app on my phone.
The worst has got to be a rashes and non-stop itching. In the first eleven days of taking high dose (high relative to the recommended 5 grams), I was scratching my limbs endlessly before bed, which affected my sleep tremendously; for a while it became a negative cycle of lacking sleep and then taking creatine to compensate for said lack of sleep. After reading online of testimonies, Reddit discussions and medical articles, I realized that my itching is a rare side effect of taking creatine. I've reduced to 10 grams, but I eventually decided to maintain 15 grams (as I'm heavy-set of 100 kilograms).
I bought this as this is the largest size I could find and that would be less expensive in the long run - coming to about 3.95 PhP per gram. I do recommend this product, and using a kitchen weighing scale to measuring your doses.