It depends how often you have used the KWs. If you use them too much then it is possible that you could suffer as a result, not by being penalised per se but by losing ranking points for over optimisation.
There is no defined rule with regard to keyword density and each expert will probably give you a different opinion. This is because they don't know for sure, keywords on the page being only a small part of the overall SEO. Google Keyword Density and take your chances with what you find there.
As I said KW density is now only a small part of SEO and the location of the KWs is more important. You will need to consider putting the KWs in places like the title element, at the start of the meta description, in H1, H2, H3, in the first paragraph, in bold or italics, in image alt tags and in outbound links, etc. All of these can help but remember that the most important factors in SEO are off site. In other words get links to your site using these KWs in the hyperlinks.
