Half Marathon Fueling: The 30-60g Carb Rule That Actually Works

Here's the practical version: aim for 30-60 grams of carbs per hour once you're racing a half marathon, and get your first gel in at 20-30 minutes—not later. Wait too long and you're playing catch-up on glycogen you can't fully recover mid-race. After that first one, take another every 30-40 minutes. For most runners that lands at 2-3 gels if you're finishing under 2 hours, or 3-4 if you're out there longer.

The reason 30-60g is the sweet spot comes down to how your gut absorbs carbs. A single sugar source (just glucose) maxes out around 60g/hour because your intestine has a limited number of glucose transporters. But glucose and fructose use different pathways to get absorbed, so pairing them lets you push more total carbs through without your stomach staging a revolt. That's why most modern gels blend the two—it's not marketing, it's transporter biology.

Water only, no sports drink. Chasing carb-heavy gels with a carb-heavy drink just stacks concentration in your gut and raises your risk of cramping or GI distress right when you can't afford it. Water dilutes the gel enough to keep things moving smoothly.

The part people skip: rehearse this exact plan—same brand, same timing—on your long runs before race day. Your gut adapts to fueling just like your legs adapt to mileage. Half marathons sit in an awkward zone where you're going hard enough that GI issues hit fast, but long enough that skipping fuel entirely will cost you in the final 20 minutes. Don't find out on race morning that a new gel flavor doesn't sit well. Test it, trust it, then run it.