GRE Scores for Graduate programs in Chemistry I am planning to apply to PhD programs in Chemistry this year so I took the GRE last week and my scores were the following:

Verbal - 161 - 88%

Quantitative - 154 - 55%

(I still don't have the scores for the Analytical Writing section)

As a foreign student, I am not familiarized with the American admission system for graduates and I'm not sure if this score is sufficient (alongside with my CV, which is not that extraordinary) to guarantee acceptance in north american graduate programs.
In your experience, should I retake the GRE and try to obtain a better score or this should be sufficient? Please note that I am not aiming super top institutions like Harvard, MIT, etc, a decent normal PhD program will be a huge improvement for my career already, since I come from a country with substandard research in chemistry.
I looked up in some institutions and it seems that the quantitative score is acceptable (verbal seems to be ok for chemistry programs), however, some institutions put the lower limit to 155 on the GRE, which is higher than my score.

Thanks in advance

PS.: I would like to retake the GRE, but I'll only do so if I judge it is extremely necessary, since it costs $215 and where I live it is a great amount of money
While I am not in Chemistry, I can tell you from a US perspective that there is no such thing as a GRE score that guarantees acceptance. As long as you are above any "minimum score" (which most places are moving away from, but many admission committees reportedly still privately use), it guarantees your GRE won't alone prevent your file from being considered, but that's really it. Even a 99% on all sections is no guarantee of admission to anywhere I've ever heard of. 

In general, higher scores are of course better, but the general advice is that retaking the GRE should only be done if you have a good reason to think you would do very differently. I retook the GRE once after a month of brushing up on some of the algrebra and geometry I had not touched in years, and it still only changed my quantitative score by just a few points. The only reason it wasn't a total waste of money is I didn't have to wonder, "gee, if I had just taken it again, would I have done much better?" I got the answer, which was no, I would not in fact do better without a lot more work that I didn't actually want to do :)

The GRE overall is pretty good at test-retest reliability, and if you prepared reasonably well (went through a practice test or two, were familiar with the type of questions being asked, were not very rusty on the topics covered) it takes considerable effort to do substantially differently. However, you can test this out for free in an afternoon by looking up the ETS free POWERPREP software (from the makers of the GRE), which allows you to simulate a full test at normal testing conditions, in the comfort of your home. If you follow the test protocol on your own (no outside source, only blank paper and a pencil, timed breaks with no food, etc) and the estimated score is not wildly different than what you got on test day, then you just have to decide if it is worth spending many hours of intense preparation to try to get better at taking the test. 

Regardless of what you end up choosing, don't let a focus on the GRE score prevent you from making the rest of your application as good as you can. A well written statement (edited and reviewed multiple times) and working with your letter writers to get good letters (delivered on time) is essential, while extra points on a test are just "nice to have".