Yes. Lemon peel is edible and is not bad for you in the amounts people normally eat, which is why grated lemon zest is a common baking and cooking ingredient. It is actually more nutrient-dense than the fruit’s flesh: USDA data list 100 grams of raw lemon peel at about 47 calories, 10.6 grams of fiber, 129 milligrams of vitamin C and 134 milligrams of calcium, compared with 2.8 grams of fiber and 53 milligrams of vitamin C in the same weight of peeled lemon.
The peel is bitter, especially the white pith under the yellow skin, so most recipes use only the thin outer zest. Rinse the lemon well before zesting, as you would any produce eaten with its skin.
Source: Lemon peel, raw, USDA FoodData Central
Image: Lemon zest by Rebecca Siegel, CC BY 2.0, via Wikimedia Commons.