How long does ketoacidosis take to leave

I am 16 years old and in an hour I have an excursion, I got up with 250 will I be fine by then?On the excursion I will have to walk.

You don't give many data so I tell you a little in general.That you have the high glucose does not imply that there are ketones.And that there are ketones either means that there is ketoacidosis.To have ketoacidosis you have to have ketones at 3 or more.Less than 0.6 is normal and if it is more than 0.6 it would be necessary to start measures so that it does not end in a ketoacidosis.These are the reference values:

Less than 0.6 mmol/L: normal or negative.
0.6 - 1.0 mmol/L: slightly elevated.
1.1 - 3.0 mmol/L: Risk of ketoacidosis.
> 3mmol/L: Go to emergency service.

Here are more information than it is and how to act before a ketoacidosis:

Link

If you do not have ketones and you have corrected with extra insulin to download 250, as soon as you take effect you should be in normal values ​​and you can walk without problems.When walking will also make insulin more effect so be careful not to give you a downturn.Always carry something with sugar to take justice and the glucometer to check how you are going.
If you have not been able to look at the ketones, control the glucose during the excursion to correct with fast insulin if you need it.As soon as you are in normal glucose values ​​you don't have to worry.In the link that I have put you also come the symptoms of a ketoacidosis, if you notice any of them and you have not been able to lower the glucose call for emergencies and tell you what to do.And if the glucose is fine but you continue noticing symptoms of ketoacidosis also calls emergencies, with normal glucose levels there should be no problem but just in case.
But well, you don't be alarmed every time you see a higher glucose value than 200 because it sometimes passes without explanation.In those cases you click quickly to correct it and look at the glucose at 2 hours to see what has come down.If no one has explained to you how to correct you have to ask the endocrine or the educator to teach you and tell you also to do if you suspect that you have ketoacidosis.
In the forum you can also ask what you want and we will try to help you in what we can.