Hi Cat, there are a few things you could go for that wouldn't be too awful, though there isn't anything truly wonderful. The problem really is with the rice/noodles/extras. How about one of these...
Chinese: Beef or chicken with mushrooms, and swap the rice for stir-fried beansprouts.
Indian: Tandoori mixed grill with vegetable curry instead of the usual extras.
Of course you could improve on the carb count of these by making your own, but (a) you're poorly, and (b) it's takeaway night for goodness sake!
Hope you find something you like.