Cereal is unfortunately high in carbs (they do vary from brand to brand). You should expect your peak spike to be about 2 hours post meal. Try testing hourly and see how quickly (or not!) your levels come down. As other members say, we all learn to eat to our meter - find out what spikes us (or not). Some find that they can tolerate porridge, some not - it all seems to depend on how large a portion and how finely milled the porridge flakes are.