How long does a penis growth spurt last and when does it start? -

i am 15 and i was 5.5 like 2 weeks ago and now im like 6.25

You are fine. It can start as early as 13 and last until 16 to 18. How big you will get depends on testosterone levels. The higher the more it grows. For example. Boys with micropenia (very small penis) are treated by putting testosterone cream on the penis or by injections. Do not do this without a doctor. The best thing is to eat healthy. Fruit and veggies. Pumpkin seed and Pistachios as well as other things raise testosterone levels. Easy on the sweets. No smoking! How big you get pepends on how big your father and your mothers father is. That is the genetics that controls how high your testosterone level will get.

This sort of growth can be normal, but I would see your doctor. It can be the result of an allergic reaction that may render you sterile.

its starts like from 13 and can go on until your like 18.

what DonChuy just said is spot on, exept that it can go on for longer, depending on weather you hit puberty earlyer or later