UTMB
The Ultra-Trail du Mont-Blanc. 110 miles, 32,800 feet of climbing, three countries, one of the deepest ultra fields in the world.
UTMB swings 40F across a single day from valley afternoons to col-top nights, so sodium has to flex with the terrain. Plan 600 to 900 mg per hour as a baseline, pre-dose 600 mg sodium at each col base, and self-supply electrolyte capsules rather than relying on European aid-station mixes, which are formulated for lower-sodium sweat profiles.
UTMB Fueling Plan
For a 165 lb athlete finishing UTMB in about 35 hr, plan roughly 60 g of carbs, 550 mg of sodium (750 mg for a salty sweater) and 600 ml of fluid per hour. That is about 2,100 g of carbs and 19,300 mg of sodium across the race.
| Finish time | Carbs | Sodium | Fluid |
|---|---|---|---|
| Front of field22 hr | 60 g/hr1,320 g total | 550 mg/hrsalty sweater 750 mg | 600 ml/hr13.2 L total |
| Mid-pack35 hr | 60 g/hr2,100 g total | 550 mg/hrsalty sweater 750 mg | 600 ml/hr21 L total |
| Back of pack44 hr | 60 g/hr2,640 g total | 550 mg/hrsalty sweater 750 mg | 600 ml/hr26.4 L total |
Computed by the free sodium and carb calculators for a 165 lb athlete in mild conditions. Fluid is a planning figure for what to carry, not a drinking schedule: on the day, drink to thirst. Your own numbers move with body weight and sweat rate.
Where The Sodium Math Bends
UTMB starts at 3,396 ft, tops out at 8,415 ft at Col des Pyramides Calcaires (mile 40.9) and finishes at 3,399 ft. Cramping tends to cluster on the long climbs and the descents that follow them.
- Mile 0, Chamonix, 3,396 ft
- Mile 5.7, Les Houches, 3,310 ft
- Mile 14.2, Saint-Gervais, 2,654 ft
- Mile 20.2, Les Contamines, 3,766 ft
- Mile 29.2, Croix du Bonhomme, 8,031 ft
- Mile 32.5, Les Chapieux, 5,072 ft
- Mile 40.9, Col des Pyramides Calcaires, 8,415 ft
- Mile 43.2, Lac Combal, 6,473 ft
- Mile 45.9, Arête du Mont-Favre, 7,913 ft
- Mile 51.8, Courmayeur, 3,921 ft
- Mile 55.2, Refuge Bertone, 6,503 ft
- Mile 66, Grand Col Ferret, 8,291 ft
- Mile 72.3, La Fouly, 5,262 ft
- Mile 77.5, Praz de Fort, 3,789 ft
- Mile 81.1, Champex-Lac, 4,839 ft
- Mile 88.3, La Giète, 6,155 ft
- Mile 91.4, Trient, 4,275 ft
- Mile 93.9, Les Tseppes, 6,352 ft
- Mile 98.5, Vallorcine, 4,134 ft
- Mile 105.6, La Flégère, 6,152 ft
- Mile 109.9, Finish, Chamonix, 3,399 ft
| Climb | Miles | Gain | Avg grade |
|---|---|---|---|
| Croix du Bonhomme | 22.9 to 29.2 | 4,252 ft | 12.8% |
| Col de la Seigne and the Pyramides Calcaires | 32.5 to 40.9 | 4,321 ft | 9.7% |
| Refuge Bertone, out of Courmayeur | 51.8 to 55.2 | 2,677 ft | 14.9% |
| Grand Col Ferret | 63.2 to 66 | 2,493 ft | 16.9% |
| La Giète | 84.1 to 88.3 | 2,339 ft | 10.5% |
| La Flégère, via Col des Montets | 98.5 to 105.6 | 3,117 ft | 8.3% |
What's On Course
Fourteen refreshment points sit between start and finish. Les Houches, Checrouit, Refuge Bertone and La Flégère serve drinks only (water, cola and energy drinks); the rest add sweet and savory food, and Les Chapieux, Courmayeur, Champex-Lac and the finish serve hot meals. Bottles are refilled with water or an electrolyte drink and no cups are handed out. Crews may help only at Les Contamines, Courmayeur, Champex-Lac and Vallorcine. Cutoffs are times you must leave each point by, on the standard Friday 6:00 PM start; distances shift by a mile or so between editions.
| Mile | Station | Cutoff | Carry in |
|---|---|---|---|
| 5.7 | Les Houches (km 9.1)Drinks only | 110 g carbs, 1,000 mg sodium1,100 ml fluid over 5.7 mi | |
| 14.2 | Saint-Gervais (km 22.9)Food and drinks | 10:00 PM Fri | 160 g carbs, 1,500 mg sodium1,600 ml fluid over 8.5 mi |
| 20.2 | Les Contamines (km 32.5)Food and drinks; crew allowed | 12:00 AM Sat | 115 g carbs, 1,050 mg sodium1,150 ml fluid over 6 mi |
| 25.6 | La Balme (km 41.2)Time barrier only | 2:00 AM Sat | |
| 32.5 | Les Chapieux (km 52.3)Hot meal, food and drinks | 5:15 AM Sat | 235 g carbs, 2,150 mg sodium2,350 ml fluid over 12.3 mi |
| 43.2 | Lac Combal (km 69.5)Food and drinks | 10:00 AM Sat | 205 g carbs, 1,850 mg sodium2,050 ml fluid over 10.7 mi |
| 48.8 | Checrouit (km 78.5)Drinks only | 105 g carbs, 1,000 mg sodium1,050 ml fluid over 5.6 mi | |
| 51.8 | Courmayeur (km 83.3)Hot meal, food and drinks; crew allowed; drop bag | 1:15 PM Sat | 55 g carbs, 550 mg sodium550 ml fluid over 3 mi |
| 55.2 | Refuge Bertone (km 88.8)Drinks only | 65 g carbs, 600 mg sodium650 ml fluid over 3.4 mi | |
| 63.2 | Arnouvaz (km 101.8)Food and drinks | 6:15 PM Sat | 155 g carbs, 1,400 mg sodium1,550 ml fluid over 8 mi |
| 72.3 | La Fouly (km 116.3)Food and drinks | 10:30 PM Sat | 175 g carbs, 1,600 mg sodium1,750 ml fluid over 9.1 mi |
| 81.1 | Champex-Lac (km 130.5)Hot meal, food and drinks; crew allowed; drop bag | 2:30 AM Sun | 170 g carbs, 1,550 mg sodium1,700 ml fluid over 8.8 mi |
| 84.1 | Plan de l'Au (km 135.4)Time barrier only | 3:45 AM Sun | |
| 91.4 | Trient (km 147.1)Food and drinks | 8:00 AM Sun | 195 g carbs, 1,800 mg sodium1,950 ml fluid over 10.3 mi |
| 98.5 | Vallorcine (km 158.5)Food and drinks; crew allowed | 11:15 AM Sun | 135 g carbs, 1,250 mg sodium1,350 ml fluid over 7.1 mi |
| 105.6 | La Flégère (km 169.9)Drinks only | 2:45 PM Sun | 135 g carbs, 1,250 mg sodium1,350 ml fluid over 7.1 mi |
| 109.9 | Finish, Chamonix (km 176.9)Hot meal | 4:30 PM Sun | 80 g carbs, 750 mg sodium800 ml fluid over 4.3 mi |
Carry in is what a mid-pack average sweater (35 hr finish) uses between the previous station and this one at an even pace. Climbs take longer than their share of the distance, so carry more into a climbing section.
Source: UTMB Mont-Blanc race page course data, UTMB Live barrier times and 2026 regulations, 2025
30-75°F · moderate humidity
Climate
mild
Humidity
moderate
Cutoff
46h 30m
10-yr avg high
71°F
10-yr avg low
53°F
Record high / low
81° / 42°F
Years with rain
60%
The Cumulative Deficit Window
UTMB combines alpine altitude swings (Chamonix at 3,400 ft, the Croix du Bonhomme at about 8,000 ft), variable mountain weather, and a 30+ hour effort. The temperature can swing 40F across a single day from valley afternoons to col-top nights. Sodium planning has to flex across the climate spectrum. The combination of European drink-mix culture (less standardized than US races), language barriers at aid stations, and unfamiliar foods makes self-supplied sodium more critical than at LOTOJA or Leadville. Most US athletes underestimate the second-night cold descent into Champex where hypothermia plus sodium deficit drops a meaningful percentage of the field.
Key Considerations
- Carry self-supplied sodium capsules; do not rely on European aid station electrolyte mixes which vary widely in formulation.
- Col descents at night are the cramping windows. Pre-dose 600 mg sodium at each col summit.
- The Courmayeur to La Fouly stretch (Italy to Switzerland) is the most common drop window; sodium and fluid deficit from the previous 50 miles catches up here.
- Heat-day variant: in years with afternoon temperatures above 80F in the valleys, treat the lower segments like a hot race even if cols stay cool.
Who Finishes, And How Fast
UTMB 2026 results
Men winner · 2026
Ben Dhiman
18:16:29USA, weather reroute
Women winner · 2026
Blandine L'Hirondel
21:54:49FRA, weather reroute
Free Tools, Pre-Filled For UTMB
Tap any tool. We pre-load your event, climate, and sweat profile. Adjust your weight and finish target and the plan generates instantly.
Sodium plan
Per-hour sodium and fluid targets for UTMB conditions.
Carb fueling
Hourly carb targets and a fuel menu calibrated to your weight and the UTMB duration.
Heat protocol
10-14 day adaptation plan if you're racing into a warmer climate.
Hydration audit
Weigh-in test that converts a 60-minute training session into a measured sweat rate.
Caffeine timing
Pre-race dose, mid-race top-ups, and race-week taper protocol for UTMB timing.
Dig Into The Science
Beetroot Powder and Altitude Training: The Science
Dietary nitrate improves oxygen economy at altitude, where reduced partial pressure amplifies every performance deficit.
Stop Leg Cramps: Supplement Protocol & Risk Calculator
Leg cramps have two causes: electrolyte depletion and neuromuscular fatigue. Score yours with the free calculator, then load the 5 supplements that fix both.
Potassium for Endurance Athletes: Cramps and Targets
Potassium drives muscle contraction, fluid balance, and nerve signaling. Endurance athletes lose 100 to 300 mg per hour in sweat.
Your UTMB Plan,
Built From Real Data.
Pro unlocks a per-leg sodium, fluid, and carb schedule keyed to the actual course: Chamonix to Col du Bonhomme, Col du Bonhomme to Courmayeur, Courmayeur to Champex, and Champex back to Chamonix, dosed for each col's climb.
- Your sweat rate, from a weigh-in test or your best estimate
- Per-leg sodium, fluid, and carb schedule keyed to the course profile
- Branded, printable PDF
- Post-race feedback capture so the next plan is sharper
Per race
Every race
Unlimited race plans today. Strava connection and the multi-event calendar are still in development.
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About UTMB
Are European drink mixes compatible with my sodium plan?
Generally not. Most European aid station mixes are calibrated to French and Italian athletes, who tend toward the average to low sweat sodium profile. Salty sweaters and very-salty sweaters should self-supply electrolyte capsules and use the aid station mix as fluid plus carbohydrate, not as the primary sodium source.
How do I plan sodium across multiple alpine cols?
Treat each col as a discrete segment. Pre-dose 600 mg sodium 30 minutes before the climb base. Maintain normal hourly intake during the climb. Pre-dose another 300 mg at the summit before the descent. Most cramping happens in the first 20 minutes of the descent due to neuromuscular fatigue, not the climb itself.
Does altitude change my UTMB sodium needs?
Less than Leadville because UTMB tops out around 8,400 ft versus Leadville above 12,000 ft. Plan a 3-5% bump over your calculator output rather than 5-10%.