My son started taking Kuvan just about one month ago. He’ll be eight year’s old in May and has been classified as a hyper-phe. The Kuvan has been wonderful for him, he was permitted 375 mg phe/day and we are currently at 1500 mg phe/day and hope to increase that after this week’s blood draw. As mentioned in another post I am having a bit more difficulty getting the additonal phe into him but we are working on it. His face just lit up when he was able to eat a chicken mcnugett happy meal from McDonald’s! He has not had any issues with an upset stomach, headaches etc which are outlined as possible side affects from taking the Kuvan. He takes two pills a day, in the evening after dinner. The people with BioMarin have been fantastic to work with and took care of all of the insurance information as well.