A guide to support your plan.
Health disclaimer
Last updated: 18 October 2026
General information, not medical advice
carbs. provides general educational information about marathon carbohydrate loading and fuelling. It is not a medical device, diagnostic tool or substitute for advice from a doctor or registered sports dietitian. A target calculated from your weight is an estimate, not an assessment of your individual health or nutritional needs.
Use a plan that suits you
Your needs depend on training, race duration, health, appetite, weather and gut tolerance. Adapt suggestions to the routine you have practised. A target is not a requirement to finish a large meal, consume more than you tolerate, or ignore symptoms. Race morning is not the time to try unfamiliar products or increase intake beyond what you have trained for. Using the app cannot guarantee glycogen levels, a finishing time or a safe race.
When to get individual advice
Speak to a suitable clinician or sports dietitian before changing your intake if you have diabetes, kidney or heart disease, a gastrointestinal condition, a history of disordered eating, are pregnant or breastfeeding, or take medication that affects fluid balance or blood glucose. The app is intended for adults; younger athletes need age-appropriate professional guidance.
Food estimates and allergies
Food and drink values, portion illustrations, meal ideas and barcode results are approximate and can be incomplete or incorrect. Check current packaging and serving sizes. The app does not check allergens, intolerances, interactions or whether a food suits your dietary requirements. Total carbohydrate and fluid needs should include all relevant foods, gels and drinks.
Hydration needs vary
Hourly fluid ranges are broad guidance, not a prescription. Follow an individual plan practised in similar conditions, taking account of thirst and sweat losses. Do not force fluids to meet a number or drink more than you lose through sweat. Excess fluid intake can be dangerous; electrolyte products do not make overdrinking safe.
If you feel unwell
Stop exercising and seek help if you feel unwell. Chest pain, collapse, confusion, severe breathing difficulty or other serious symptoms require urgent medical attention from race medical staff or emergency services. Do not rely on the app to assess symptoms or decide whether it is safe to continue.
Sources and questions
Where practical, guidance in the app links to its source. Recommendations may evolve and may not suit every runner. Read our Terms of service and Privacy policy. For questions about the app, contact carbsdotrun@gmail.com; this address does not provide medical care or emergency support.