I personally took 3 IU's a day at 40 year old and this actually caused major water retention that was very noticable to other people. I went to divided dosages (2-3x day) and this helped but did not eliminate the problem.
I have heard many reports of people using double this amount. Start with 1-2 IU's a day and work your way up slowly. If you run into any kind of side effects drop back the amount and wait for the sides to go away. You can then increase the dosage.