How much Sodium and Potassium do you need to Rehydrate? Perimenopause Training | Dr. Stacy Sims

Sims contrasts this targeted formula with commercial sports drinks, which are designed to supply fuel during exercise, not to optimise rehydration afterward. Gatorade at 6% carbohydrate, for instance, creates too high an osmotic pressure in the small intestine; this forces the body to draw water from the bloodstream and interstitial spaces into the gut to dilute it, resulting in delayed rehydration and even dehydration. Plain water, conversely, requires the body to secrete its own sodium and glucose into the intestine before absorption can occur, slowing the process. The prescribed 360–400 mg sodium and 200 mg potassium per 16 oz, with an optional 2% carb, sits in the ‘sweet spot’ of osmotic balance, harnessing the intestine’s built-in glucose-sodium transporters for rapid fluid uptake without the counterproductive fluid shifts. For prolonged efforts, a slight bump to 3–4% carb supports energy while remaining within the safe osmotic window.

Sims asserts that for healthy individuals eating regular meals, electrolytes from food are sufficient. She explains that the body’s fluid transport system relies on sodium and potassium, not a broad “electrolyte cocktail.” The term “replacement” implies a deficit that rarely exists outside of prolonged sweating or illness. By decoupling electrolyte consumption from daily hydration, she empowers people to save money and focus on whole-food sources, while using simple sodium/potassium additions only when rehydration is truly needed.

Sims explains that estrogen and progesterone modulate AVP, the hormone that stimulates thirst and promotes water retention. Estrogen moderates plasma osmolality, the driver for AVP release. As estrogen declines, the body’s set point shifts — low plasma osmolality may no longer trigger a strong thirst drive, and instead the body may crave sodium without prompting water intake. By late perimenopause, the hormone dysregulation causes a noticeably muted thirst sensation. Consequently, women must become intentionally conscious about drinking fluids with sodium and potassium, especially after exercise, rather than relying on natural thirst cues.