Malaria treatment and prevention (Nairobi)

Hello,
I will be in Nairobi for one month, and I am considering how to go about Malaria risks. The standard medical advice here in the Netherlands is always to take profylaxis. However, if the risk on malaria is not too high, I would prefer not to take profylaxis as it has many side effects, costs, and induces resistance among malaria mosquito's. I would much rather have a stash of malaria medication, and take this as soon as I would experience any signs of malaria. I read somewhere that the malaria prevalence in Nairobi is not that high, is that true? I wonder what your own strategies are, for those that are staying in Nairobi or other places for longer periods of time?

It goes without saying that any comments on these questions by me or anyone else should and will not be interpreted as medical advice :). I am simply interested in your own ideas about this.

Kind regards,
Caspar