I am currently using my monthly contact lenses and it has not reached its 30 days period yet but my solution ran out, and so I bought another brand. Is it okay to just switch? Will it hurt?
To change the brand of solutions you should do what is called " purging" the lenses.
Put your lenses in the new solution for 2 hours, then throw it out, then again for 2 hours, and throw it out...then again for the night.
By morning, all traces of the old solution will be gone from the lenses and you won't have any problems.Sometimes it can cause a lot of irritation if that isn't done first.
Many solutions can cause an interaction with the different ingredients.
Another brand or another bottle?
Another bottle of the same brand is definitely okay; that's kind of a no-brainer.
Another brand makes things tricky; we usually recommend you don't, but it's really hard to time these things. As long as it's something similar -- i.e. a rub-and-rinse multipurpose soft lens cleaner -- it should be fine, just double-check the instructions! You might find, though, that you have some irritation or dryness with the new solution; that's because different brands of solutions and contacts interact differently, and it's mostly a trial-and-error process, even for those of us who work with the products every day.
In any case, it won't be painful, and worst-case scenario, it gives you trouble, you go to your eye doctor, and they figure out a better solution for you to use.