How old do I have to be to run a marathon?

I'm 17 and a senior in high school. I run religiously and consistently run half marathons in under an hour and a half. I back pack a lot and I'm really big on endurance sports. I'm planning on biking for 24 hours straight in an attempt to beat my dads mileage count of 205. I really think it would be cool to do a marathon before I hit 20, but I don't want to do anything stupid and ruin myself early.|||im 17 also and just finished running a marathon. It depends on the race some don't have age limits, others you have to be 18.|||It varies by individual race. The limit for most is age 18 by race day.





Some will allow under age 18 by at least a year or two with parental consent.





It is indeed usually recommended that those who are younger avoid marathons though due to detrimental impact on still developing bodies, and a full marathon can be a lot more negative than a half. The risks generally far exceed the rewards, and those who are younger are usually encouraged to develop speed while they can rather than spend extensive time in distance training and missing out on the other opportunities of youth.|||Also, it depend where you live.. I live in Ireland, and Athletics Ireland doesn't allow under 18s to race any distance farther than 6 miles, which I personally think is a bit too extreme, but I can see their point! I also went through a stage of wanting to run a marathon, but I decided to focus on my shorter races now, like 5ks. I figure you may as well become the best you can be at shorter races, and leave the marathon for a few years. If you start now, you may be hit by the 'marathon bug' and decide to run one every year, which means that you will be starting to put stress on your joints earlier in life!!|||Most marathons will accept you at 18, and many will accept you younger if your parents sign off.





however, I would strongly recommend waiting until you are fully grown and have stopped growing for almost a year. A marathon (and the training associated with it) is very hard on a young person's body.





It is true that training for 5k can incorporate runs of marathon length, but there is a world of difference of doing a 30 mile run at long, slow distance pace and being involved in an actual marathon.





Good luck.