Is there any evidence that bitter melon and cinnamon help to lower blood glucose level?

Yes, see below:: Yes, there is evidence that both of these are effective in lowering blood sugar. Most of the studies on bitter melon are animal studies so more research is needed but many have found it effective- see http://tinyurl.com/zygunvx and look at the 2013 article it links to. The evidence on cinnamon is more contradictory. Like all medicines, it helps some more than others: http://tinyurl.com/h8h29fj