Sodium loss in ultras varies by athlete (light sweater: 400 mg/hr; heavy sweater: 1,500 mg/hr) and by conditions (mild: 500 mg/hr target; hot: 800–1,200 mg/hr). The mix you choose has to deliver that sodium without ruining your stomach. Below: the five we'd actually carry, ranked.
The picks
LMNT
LMNT Recharge Electrolyte Drink Mix
The industry gold standard for high-sodium ultra fueling. 1,000mg sodium per packet — the right number for hot races. Zero sugar means it pairs with whatever carb source you choose.
- 1,000 mg sodium per packet
- 200 mg potassium · 60 mg magnesium
- Zero sugar — works with gels
- Four flavor lineup (Citrus, Raspberry, Watermelon, Orange)
Skratch Labs
Skratch Labs Sport Hydration Mix
The mix you'll actually use in training. 380mg sodium + 80 cal of carbs per serving. Mild flavor, easy on the gut for hours of running.
- 380 mg sodium · 80 cal carbs per serving
- Real fruit flavoring — easy to drink for hours
- Made in Boulder, CO
- Pairs with gels for full-spectrum fueling
Skratch Labs
Skratch Labs Hyper Hydration Mix
Pre-race load mix. 1,720mg sodium per serving — the highest in the category. Drink one in the morning before a hot race; your blood plasma volume thanks you for the next 8 hours.
- 1,720 mg sodium per packet
- Pre-race load (drink 60–90 min before start)
- Critical for races above 75°F
- Lab-tested ratios
Tailwind
Tailwind Endurance Fuel
The original "drink your calories" mix. 200 cal of carbs + 310 mg sodium per scoop, no extra food needed. The full strategy for runners who can't stomach gels.
- 200 cal carbs + 310 mg sodium per scoop
- No artificial flavors
- Drink-only fueling — no gels needed
- Real-food gut friendly
SaltStick
SaltStick FastChews
Chewable salt tabs for when liquid sodium isn't enough. 200mg sodium per chew, great backup for hot canyon sections. Always 4–6 of these in every drop bag.
- 200 mg sodium per chew
- Chewable — no water needed
- Citrus / fruit punch flavors
- Perfect drop-bag insurance
Sodium math by race
The basic equation: target sodium (mg/hr) = your sweat rate × your sodium concentration. Without lab data, use these defaults:
- Cool race (under 65°F): 400–600 mg/hr
- Mild race (65–75°F): 500–800 mg/hr
- Warm race (75–85°F): 700–1,000 mg/hr
- Hot race (85°F+): 800–1,500 mg/hr (and pre-race Skratch Hyper Hydration)
Adjust up if you notice white salt rings on your singlet at the end of training runs. Adjust down if you cramp up despite high intake (common — over-sodium-ing is real).
The heat-day cheat code
Pre-load with Skratch Hyper Hydration 60–90 minutes before a hot race. The 1,720mg sodium load expands plasma volume, which buffers you for the first ~3 hours and makes the early miles much more sustainable. This is the single most cost-effective race-day intervention: $4 to drink, $0 to administer, real measurable difference.
What we don't recommend
Gatorade Endurance: sodium content is too low (200 mg/serving) for ultras and the high-sugar formulation upsets stomachs late in races. Fine for marathons, wrong tool for 100-milers.
Pedialyte: excellent post-race recovery; not a race-day fueling source. Sodium is right but carb load is too low for active fueling.
Plain water: dilutes blood sodium, accelerates hyponatremia. Don't drink water-only past hour 2 of a race in any conditions.