I heard that urinating whilst standing is not permissible in Islam, so I left that practice. However I have a little problem when preparing to do wudu. When I urinate while not standing in toilets, I rarely get all my urine out. This causes me to sometimes break my prayer to redo wudu again because I feel that urine drops are coming out. Maybe this is because of a habit, but I want know if it is really forbidden.
No it is not obligatory to urinate standing up, but it is Sunnah to urinate sitting down.
It was narrated that 'Aishah said: "Whoever tells you that the Messenger of Allah (ﷺ) urinated standing up, do not believe him, for he would not urinate except while squatting."
The Prophet did so because this was more concealing, and it reduces the risk of any drops of urine splashing up onto his body or clothes.
Another hadith showing you can urinate while standing:
It was narrated from Hudhifah that the Messenger of Allah (ﷺ)came to some people's garbage dump and urinated while standing.
In this case, the Prophet urinated while standing perhaps because he was in a place where he was unable to sit down, or he did that to show the people that it is not haram.
1- It is not haram to urinate while standing.
2- It is preferable but not a must to sit while urinating because it is Sunnah and there is no risk of drops of urine splashing onto your body or clothes, and it does not expose your private part.
As salaamu alaikum All praise be to Allah We seek his aid and ask for his guidance. It is not wajiib to urinate while sitting, but it is Sunnah(Mus'tahab) to do so to avoid the possibility of urine splashing on you or your garments and not exposing your awrah. If you are using a public bathroom, the I would recommend that you use a stall. This will decrease the possibility of exposing your awrah. Wa Allahu a'lim