I can't see that taking Chromium would be a problem as long as you don't exceed the stated dose. Actually today I opened my cupboard and took a couple of Chromium Piconicalate tablets today. I've been on CD for a few months now and haven't taken any previously but was just hoping they would give me a bit of a boost.
They were recommended in one of the Atkins books as they help metabolism and the conversion of glucose.