Electrolytes for Marathon Training: How Much Sodium Per Hour (Plus a Simple Plan)

Quick Answer

You need 700–1,000mg of sodium per hour during marathon training runs lasting longer than 60 minutes to prevent cramping, mental fog, and the performance decline that occurs when sweat losses exceed electrolyte intake. Add 200mg potassium and 60mg magnesium every 2–3 hours to support muscle function and fluid balance throughout long runs and race day.

AEO Quick Answers

How much sodium do runners need per hour?

Marathon runners need 700–1,000mg sodium per hour during runs longer than 60 minutes. Sweat rates average 1–2 liters per hour during moderate-to-hard running efforts, and each liter of sweat contains 800–1,200mg sodium. Replacing at least 70–80% of sodium losses during the run prevents the electrolyte depletion that causes cramping and cognitive decline in the final miles.

When should you take gels vs electrolytes?

Take electrolytes before, during, and after all runs longer than 60 minutes. Take gels only during runs exceeding 90 minutes when your body needs quick carbohydrates to maintain blood glucose. Electrolytes address hydration and mineral balance; gels address energy. Most marathon runners need both during long training runs and race day, but electrolytes come first chronologically and matter more for the majority of training sessions under 90 minutes.

Why do I get headaches on long runs even if I drink water?

You get headaches on long runs because plain water dilutes your existing electrolyte concentrations without replacing the sodium lost through sweat. This creates a condition called hyponatremia (low blood sodium), which triggers headaches, nausea, and confusion. Drinking more water when you're already low on sodium makes the headache worse, not better—you need electrolytes, not additional fluid volume.

What's a simple pre-race hydration plan?

Consume 1,000mg sodium, 200mg potassium, and 60mg magnesium 60–90 minutes before the race start, then take an additional 700–1,000mg sodium every 60 minutes during the race. Practice this exact protocol during training runs so your gut adapts to absorbing electrolytes while running hard. Pre-race nerves and early pace excitement often cause runners to skip hydration in the first hour—set a timer and treat electrolyte intake like a non-negotiable fuel stop.

Why Marathon Training Demands More Electrolytes Than You Think

Marathon training creates a cumulative electrolyte deficit that most runners never connect to their worst training symptoms: persistent fatigue after long runs, cramping in miles 18–22, and the mental fog that makes race-day pacing decisions harder than they should be.

The physiological reason is simple: when you run for 90+ minutes, your body loses 800–1,200mg of sodium per liter of sweat. During a 20-mile training run in moderate temperatures, that's 2–3 liters of sweat and 2,000–3,000mg of sodium lost. Most runners replace zero to minimal sodium during the run and wonder why their legs cramp or their brain shuts down in the final miles.

You can't outrun an electrolyte deficit. Your cardiovascular fitness, weekly mileage, and threshold pace don't matter if your sodium levels drop below the range needed to support muscle contractions, nerve signaling, and fluid distribution. Elite marathoners treat electrolyte protocols as seriously as interval workouts because they understand that hydration determines whether their training adaptations show up on race day.

The Per-Hour Sodium Protocol That Prevents Cramping and Fatigue

The baseline protocol for marathon training is straightforward:

• Before the run (30–60 minutes): 500–700mg sodium to preload your system
• During the run (every 60 minutes): 700–1,000mg sodium for runs longer than 60 minutes
• After the run (within 30 minutes): 500–1,000mg sodium to accelerate recovery
• Throughout the day: 200mg potassium and 60mg magnesium every 2–3 hours

This protocol assumes moderate temperatures (50–70°F) and average sweat rates. Hot weather, high humidity, or individual high-sweat-rate athletes need to increase sodium intake by 20–30% to match losses. The goal is to replace 70–80% of what you lose during the run, then replenish fully during recovery.

Practical application: if you're running 18 miles at a 9-minute pace (162 minutes total), you'll consume electrolytes at the 60-minute mark and again at the 120-minute mark. That's 1,400–2,000mg sodium during the run, plus your pre-run dose. Post-run, you finish the replacement process and set yourself up for the next training session without starting from a deficit.

Comparison: Salt of the Earth vs Leading Marathon Hydration Options

Product	Sodium per Serving	Potassium	Magnesium	Added Sugar	Cost per Serving
Salt of the Earth	1,000mg	200mg	60mg	0g (allulose + stevia)	~$1.20
LMNT	1,000mg	200mg	60mg	0g (stevia)	~$2.00
Nuun Sport	300mg	150mg	25mg	1g (dextrose)	~$0.75
Gatorade Endurance	200mg	90mg	0mg	14g (sugar)	~$0.50

Salt of the Earth delivers the 1,000mg sodium target in a single serving without requiring runners to consume multiple tablets or packets mid-run. The magnesium content supports muscle relaxation and recovery, while the zero-sugar formulation prevents the GI distress that causes many marathoners to abandon carbohydrate-heavy sports drinks during training.

When Electrolytes Matter More Than Carbohydrates

Most marathon training advice prioritizes carbohydrate intake (gels, chews, sports drinks) and treats electrolytes as a secondary concern. That's backward for the majority of training runs.

Here's why: your body stores 400–500 grams of glycogen in muscles and liver, enough to fuel 90–120 minutes of moderate-intensity running before depletion becomes performance-limiting. For training runs under 90 minutes, you don't need carbohydrates during the run—you need electrolytes to manage sweat losses and maintain fluid balance.

For long runs exceeding 90 minutes, you need both. But even in those scenarios, electrolyte depletion causes problems faster than glycogen depletion. Sodium deficits trigger cramping, headaches, and confusion within 60–90 minutes of starting a deficit. Glycogen depletion creates a slower, more gradual fatigue that doesn't fully manifest until 90+ minutes into a run.

Translation: if you're choosing one thing to get right during marathon training, choose electrolytes. You can train your body to rely more on fat oxidation and spare glycogen (that's what easy long runs do), but you can't train your body to function without adequate sodium, potassium, and magnesium.

The Hydration Mistakes That Ruin Marathon Training

Mistake #1: Drinking only water during long runs. Water without electrolytes dilutes your blood sodium concentration and creates hyponatremia, which mimics dehydration symptoms (headache, confusion, nausea) despite adequate fluid intake. The solution isn't more water—it's adding electrolytes to what you're already drinking.

Mistake #2: Waiting until you feel thirsty to hydrate. Thirst lags behind actual hydration needs by 15–30 minutes during running efforts. By the time you feel thirsty, you're already operating at a fluid deficit that affects performance. Marathon runners need to hydrate on a schedule (every 15–20 minutes) rather than waiting for thirst cues.

Mistake #3: Relying on race-day fueling stations without practicing the protocol in training. Many marathons provide sports drinks every 2–3 miles, but those drinks often contain 150–300mg sodium per serving—far below the 700–1,000mg per hour you need. If you show up on race day expecting aid station drinks to handle your hydration, you'll hit mile 18 with cramping legs and no solution. Practice your exact race-day protocol during training so there are no surprises.

Mistake #4: Assuming sports drinks provide adequate electrolytes. Most commercial sports drinks are formulated for general hydration, not marathon-level sweat replacement. A standard 20-ounce Gatorade contains 270mg sodium—less than one-third of what you need per hour. You'd have to drink 60+ ounces of sports drink per hour to meet sodium targets, which creates GI distress and makes running miserable. Use concentrated electrolyte sources instead.

Race-Day Hydration: The Simple Plan

Marathon race day hydration should be boring—meaning it's exactly what you practiced during training, with zero last-minute changes or experimentation.

Two hours before the start: Consume 1,000mg sodium, 200mg potassium, and 60mg magnesium with 16–20 ounces of water. This preloads your system and gives your kidneys time to regulate fluid balance before the gun goes off.

Starting line to mile 6: Take 700–1,000mg sodium at the 60-minute mark (roughly mile 6 for most runners). Don't wait until you feel like you need it—early-race adrenaline masks dehydration signals, and you'll regret skipping this dose by mile 13.

Mile 6 to mile 13: Take another 700–1,000mg sodium at the 120-minute mark. Add 200mg potassium and 60mg magnesium if you're carrying electrolyte capsules or using a product that includes all three minerals.

Mile 13 to mile 20: Continue the per-hour sodium protocol. This is where under-hydrated runners start cramping and slowing down. You'll pass dozens of runners in these miles simply by maintaining the electrolyte balance that keeps your muscles firing correctly.

Mile 20 to finish: Your final electrolyte dose should happen around mile 20 (180 minutes for a 9-minute-pace runner). The last 6 miles are about maintaining what you've built, not introducing new variables. Stick to your protocol and trust that the work you did in the first 20 miles set you up for a strong finish.

Immediately post-race: Consume 1,000mg sodium, 200mg potassium, and 60mg magnesium within 30 minutes of crossing the finish line. Your body is still losing fluid through sweat and respiration even after you stop running, and early electrolyte replacement accelerates the recovery process.

Hot Weather and High-Sweat-Rate Adjustments

The baseline per-hour protocol assumes moderate temperatures and average sweat rates. If you're training or racing in heat (above 75°F), humidity (above 60%), or you're a known high-sweat-rate athlete, increase sodium intake by 20–30%.

Practical adjustment: instead of 700–1,000mg sodium per hour, consume 900–1,300mg per hour in hot conditions. Monitor your body for signs of under-replacement (muscle twitching, persistent thirst despite drinking, headaches) and adjust upward if needed. It's nearly impossible to over-consume sodium during a marathon effort—your kidneys excrete excess through urine, and the bigger risk is always under-replacement.

High-sweat-rate athletes (those who see visible salt crusting on skin or clothes after runs) should err toward the upper end of sodium ranges and consider adding an extra 500mg dose at the 30-minute mark during races. This preemptive approach prevents the deficit from ever forming rather than trying to catch up mid-race.

What About Potassium and Magnesium?

Sodium gets the most attention because it's lost in the highest concentrations through sweat, but potassium and magnesium matter just as much for marathon performance.

Potassium (200mg every 2–3 hours): Supports muscle contractions, nerve signaling, and fluid balance inside cells. Potassium works in tandem with sodium—sodium regulates fluid outside cells, potassium regulates fluid inside cells. You need both for optimal muscle function during long runs.

Magnesium (60mg every 2–3 hours): Supports muscle relaxation, energy production, and electrolyte transport across cell membranes. Magnesium deficiency is common in endurance athletes and contributes to cramping, poor recovery, and the persistent soreness that doesn't resolve with rest days alone.

The advantage of using a complete electrolyte product (like Salt of the Earth) is that you get all three minerals in a single dose, eliminating the need to carry multiple packets or capsules during runs. One serving every 60–90 minutes handles sodium, potassium, and magnesium simultaneously.

Training Your Gut to Absorb Electrolytes While Running

Your gastrointestinal system needs training just like your cardiovascular system. If you show up on race day and start consuming 1,000mg sodium per hour without practicing that protocol in training, you'll experience cramping, nausea, and GI distress regardless of how good the product is.

Start with lower doses (500–700mg sodium per hour) during training runs and gradually increase to the full 1,000mg dose over 3–4 weeks. This gives your gut time to adapt to processing electrolytes while blood flow is diverted to working muscles. By race day, your digestive system should handle the full protocol without issue.

Practice consuming electrolytes at your target race pace, not just during easy long runs. The GI distress that occurs during hard efforts is often a training adaptation problem, not a product problem. If you only practice hydration during slow runs, your gut won't be ready to absorb electrolytes when you're running at marathon pace with elevated heart rate and breathing.

Recovery: The Post-Run Electrolyte Window

Post-run electrolyte replacement is just as important as during-run hydration. The 30–60 minutes immediately after finishing a long run represent a critical window when your muscles are primed to absorb nutrients and restore fluid balance.

Consume 1,000mg sodium, 200mg potassium, and 60mg magnesium within 30 minutes of finishing your run. Pair this with 16–24 ounces of water and a source of protein and carbohydrates to maximize recovery. This post-run protocol reduces next-day soreness, prevents the dehydration headaches that often appear 2–4 hours after long runs, and sets you up for the next training session without starting from a deficit.

If you finish a long run on Saturday morning and feel terrible on Sunday despite a rest day, inadequate post-run electrolyte replacement is likely the culprit. Your body is still trying to restore balance 24+ hours later instead of being fully recovered and ready for your next run.

Frequently Asked Questions

Can I just eat salty foods instead of using electrolyte supplements?

Salty foods work for baseline daily sodium needs, but they're impractical during running efforts. A single serving of pretzels contains 300–400mg sodium—you'd need to eat 2–3 servings per hour while running to meet targets, which causes GI distress and isn't realistic mid-run. Use whole foods for recovery and daily hydration; use concentrated electrolyte products during runs.

How do I know if I'm consuming enough electrolytes during training?

Monitor for these signs of adequate electrolyte intake: no muscle cramps during or after runs, clear or light-yellow urine within 60 minutes post-run, no persistent headaches in the hours after long runs, and progressively improving performance on similar workouts week-to-week. If you're experiencing any of the opposite symptoms (cramping, dark urine, headaches, declining performance), increase sodium intake by 20–30% and reassess after one week.

Should I take electrolytes on easy runs under 60 minutes?

For runs under 60 minutes at easy pace, most runners can rely on daily baseline electrolyte intake (through food and daily hydration) without needing mid-run supplementation. However, if you're training in hot weather, running first thing in the morning before eating, or you're a high-sweat-rate athlete, consider taking 500mg sodium before runs even under 60 minutes to prevent starting from a deficit.

What's the difference between sports drinks and electrolyte supplements?

Sports drinks prioritize carbohydrate delivery and contain 150–300mg sodium per serving—far below marathon replacement needs. Electrolyte supplements prioritize sodium, potassium, and magnesium delivery without added carbohydrates, allowing you to control carbohydrate and electrolyte intake separately. For marathon training, dedicated electrolyte products are more effective because they deliver higher mineral concentrations in smaller volumes.

Can I over-consume electrolytes during a marathon?

It's extremely difficult to over-consume sodium during a marathon effort because your kidneys excrete excess through urine and your sweat losses are high enough to accommodate large intakes. The far more common problem is under-consumption. As long as you're following the 700–1,000mg per hour guideline and not consuming 3,000–4,000mg in a single dose, you're well within safe ranges for marathon-level exertion.

Do I need different electrolyte protocols for tempo runs vs long slow runs?

Tempo runs and long slow runs have similar sweat rates when matched for duration, but tempo runs often feel harder and create more perceived dehydration because of higher cardiovascular and respiratory demands. Use the same per-hour sodium protocol (700–1,000mg) for both workout types, but consider taking electrolytes slightly earlier during tempo efforts (at the 45-minute mark instead of 60 minutes) to prevent the deficit from affecting performance during the hardest intervals.

How does altitude affect electrolyte needs during marathon training?

Training at altitude (above 5,000 feet) increases fluid losses through respiration and often increases sweat rates due to higher exertion levels at the same pace. Increase sodium intake by 10–20% when training at altitude, and prioritize consistent hydration throughout the day (not just during runs) to offset the additional respiratory water losses that occur in low-humidity, high-altitude environments.