The standard studied dose _is_ 5g, but the common advice you hear in the gym community is that you will see cognitive benefits from 10-20g or more, depending on your body mass. 30g isn’t uncommon. And, many believe that 5g may be too little for optimal muscle gain, again depending on your body mass.

Adverse effects, as mentioned, are mostly GI-related, some people experience bloating especially with monohydrate. Another effect is an increase in water retention, which, in turn, means you need to drink more water. It’s generally regarded as safe for the kidneys unless you already have reduced kidney function.

So, overall, not really a big deal to take well over the studied 5g dose. Not to mention the recommended loading dose is 5g 4x daily.

It is definitely more than the standard dose. I was already taking 5g for weightlifting purposes. After some of the studies suggesting mental benefits I titrated my dose up to 30g (the high end of the studies). Just added an additional 5g per week until I hit 30. I add it in powder form to my daily protein shake-- usually in the morning. While it could be a placebo, I personally feel there's a noticeable difference. I buy in bulk so it ends up being less than $.90 a day to dose at this level. It's an extremely cheap supplement.