What’s Included?

  • What are they?
  • Why do we need them?
  • How much do I need?
  • How do we replace them?

Electrolytes are a hot topic for athletes, especially when temps are warmer, and you’re sweating a lot more. Even as temps start to decrease electrolytes are still important to keep in mind. Though it will be individualized, athletes may lose between 200 – 2000 mg/L (1 L = ~33oz) of Sodium depending on exercise duration, intensity, ambient temperature, and hydration status before and after a run. Sweat rate and sodium loss are both variable in athletes. At minimum, athletes should aim to consume between 500-700 mg/hour, but some people may need much more depending on how much they sweat. If you notice salt crystals on your skin after a run, you may need to supplement more than others.

What Are They?

Electrolytes are minerals that carry an electrical charge and dissociate in a solution into positive and negative ions. Electrolytes are tightly controlled by the body, but certain ones, like sodium and chloride, are lost in higher amounts through sweat, making this an important topic for runners. Potassium, Magnesium, and Calcium are also lost through sweat, though in much smaller amounts.

Why Do We Need Them?

Electrolytes help control the maintenance of physiologic body functions, cellular metabolism, neuromuscular function, and osmotic equilibrium. In simple terms, they help direct movement of fluids in and out cells for hydration status, aid in muscle contractions (which consequences may include cramping), and generating energy.

Sodium (Na+)

  • Functions: Helps aid in movement of fluid in the body and maintaining plasma/blood volume; helps allow glucose, amino acids and other nutrients into the cell for energy
  • Low sodium: Headaches, dizziness, extreme fatigue, restlessness, decreased reflexes, muscle cramps

Potassium (K+)

  • Functions: Maintains water balance, osmotic balance, helps regulate neuromuscular function
  • Low potassium: Muscle weakness, cramping, overall weakness, cardiovascular problems

Magnesium (Mg2+)

  • Functions: Many energy pathways require magnesium. It’s important in bone metabolism as well as for the nervous system and cardiovascular system
  • Low magnesium: Muscle weakness, muscle cramping

Calcium (Ca2+)

  • Functions: Needed for nerve transmission, muscle contractions, bone metabolism, blood pressure regulations, and blood clotting.
  • Low Calcium: Numbness, tingling, cramping, lethargy, muscle weakness, confusion

How Much Do You Need & Where Can You Get Each of Them?


  • Sources: Table salt, processed foods, vegetables, grains
  • How much do you need? 1200-1500 mg/day + replacing sodium lost from exercise/sweating which should be individualized


  • Sources: table salt, processed foods, some vegetables, grains
  • How much do you need? 2300 mg


  • Sources: fruits, vegetables,
  • fresh meat, and dairy
  • How much do you need? 4700 mg/day


  • Sources: leafy greens, legumes, whole grains
  • How much do you need? 310-420 mg/day


  • Sources: dairy, green vegetables, nuts, beans, calcium enriched tofu, and calcium enriched plant based milks
  • How much do you need? 1000-1300 mg/day

Electrolyte Supplements

When sweat losses are high, supplementing on the run and after is necessary to help avoid excessive losses of electrolytes that can lead to dehydration, muscle cramping, and fatigue. Individual needs can influence what electrolyte supplements are used and how much are needed. Below are some common products that may be used (but not limited):

Conducting a Sweat Test

  • Weight before run – weight after run = fluid lost
  • Each pound lost x 16 oz = amount of fluid lost
  • Water intake during exercise – water lost during exercise / time spent exercising = fluid needed during exercise

    Final Note:

    Determining fluid and electrolyte needs should be individualized. More is not necessarily always better. Fine tuning your electrolyte intake during longer efforts can help avoid dehydration, prevent GI distress and muscle cramping, and offset fatigue.

    Amy Haas
    Run with Aim, LLC
    UESCA Certified Running Coach
    NASM Certified Personal Trainer
    NASM Certified Nutrition Coach

    Katelyn Biros, RD
    Registered Dietitian