Hi Tia,
I don't know about the supplement part but what you describe sounds like carb withdrawal to me. Although I haven't heard of it lasting for 3 weeks. I guess it's possible. Still it's quite a change for your system to go from vegetarian to Atkins. I do remember reading somewhere that calcium is one of the things your body loses a lot of when starting a low carb plan.

I'm not on Atikins by the way, I do the Carbohydrate Addicts Lifespan program. It's similar to Atkins except that once a day we eat a balanced meal that includes carbs. I'm returning to this way of eating after spending two year putting back on the 30 pounds I orginally lost.

That's a great loss for 3 weeks. Congratulations!

Dar