When collagen supplements enter your body, it needs to be broken down by your stomach acids into amino acids which your body can accept. So, taking collagen on an empty stomach should not cause any harm for most people. However, if you have a frail digestive system, it’s better if you take collagen alongside food or gulp it down slowly with your favorite fruit smoothie. But, if you absolutely want to take collagen on an empty stomach, try it once or twice to see what happens. If you’re feeling fine, have no sign of stomach problems, or aren’t sensing nauseous, then have at it. Create your collagen schedule and stick to it.