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Draft: not yet reviewed by a clinician

Use this page to prepare questions for your care team. It does not replace their advice. Your own targets and doses come from your nephrologist, diabetes team and renal dietitian.

Potassium leaching

In short

"Leaching" means cooking a vegetable in water and throwing the water away, so some of its potassium goes down the drain. Potatoes, sweet potatoes, carrots, beets and winter squash are the usual targets. Cutting them small and boiling them, then draining, removes about half of the potassium; shredding removes more. Soaking raw pieces in cold water does almost nothing, and baking, roasting, microwaving or frying removes none (Bethke and Jansky 2008). A leached potato still has potassium, so it still counts toward your day: "Since leaching does not remove all the potassium, you still must limit the amount of leached high-potassium vegetables you eat" (NKF). You only need this if your team has asked you to limit potassium.

Your numbers

Potassium before leaching, per ½ cup unless stated (USDA FoodData Central):

Vegetable Potassium
Potato, boiled, peeled, not leached 256 mg
Potato, leached or double-boiled about 130 mg, an estimate: boiling small pieces removed about half (Bethke and Jansky 2008), and leaching never removes all of it (NKF)
Potato, baked with skin, 1 medium 926 mg (baking removes none)
Sweet potato, baked 475 mg
Butternut squash, baked 293 mg
Beets, boiled 259 mg
Carrots, boiled 183 mg

What each method removes:

Method Potassium removed
Soaking raw pieces in cold water, no boiling almost none (Bethke and Jansky 2008)
Boiling ½-inch (1 cm) cubes, then draining about 50 % (Bethke and Jansky 2008)
Boiling shredded potato, then draining about 75 % (Bethke and Jansky 2008)
Double-boiling thin slices, small dice or shreds 50 % to up to 72 % (DaVita)
Soaking first, then boiling no more than boiling alone (Bethke and Jansky 2008)
A 5–10 minute soak in just-boiled water 10–20 % for potatoes and other tubers; 30–49 % for leafy greens, other vegetables, grains, meat and fish (de Abreu 2023)
Baking, roasting, microwaving, frying none

Boiling also removed some phosphorus from the potatoes (Bethke and Jansky 2008).

What to do: two methods

  1. Peel the vegetable and cut it into small pieces (about ½ inch / 1 cm cubes), thin slices, or shred it.
  2. Boil in plenty of unsalted water.
  3. Drain and throw the water away.
  4. Boil again in fresh unsalted water until soft (about 30 minutes or less in total).
  5. Drain again, then season, mash or pan-fry.

(DaVita; AKF: double-cook potatoes; Bethke and Jansky 2008.)

  1. Peel and keep the vegetable in cold water so it does not darken.
  2. Slice it ⅛ inch thick.
  3. Rinse in warm water.
  4. Soak for at least 2 hours in warm unsalted water, using 10 parts water to 1 part vegetable. If you soak longer, change the water every 4 hours.
  5. Rinse again in warm water.
  6. Cook in 5 parts fresh unsalted water to 1 part vegetable, and throw the water away.

(NKF.) Newer studies suggest the boiling, not the soaking, does most of the work (Bethke and Jansky 2008; DaVita), so the double-boil is a fine shortcut.

A short hot soak. KDIGO notes that soaking foods for 5–10 minutes in water that has just boiled "can effectively reduce the potassium by half for some foods" (KDIGO 2024). In the study behind it, that worked best for leafy greens, grains and meat, and least for potatoes and other tubers (de Abreu 2023). For potatoes, double-boil.

Checklist

  • Ask whether you need to leach at all. If your potassium is normal, you do not.
  • Use leaching for potatoes, sweet potatoes, carrots, beets and winter squash.
  • Cut small or shred: more surface means more potassium in the water.
  • Always throw the cooking water away; never use it for soup, gravy or sauce.
  • Count a leached ½ cup of potato as about 130 mg of potassium, and keep to ½-cup portions if your potassium is limited.
  • Remember that fries, hash browns, baked potatoes and potato chips are not leached.
  • Drain the liquid from canned vegetables too, and do not use it (NKF).

Examples

  • Mashed potatoes: double-boil ½-inch cubes, mash with unsalted butter and a little unsweetened almond milk instead of milk.
  • Home fries: double-boil diced potato until just tender, drain well, then brown in a pan with oil, onion and paprika.
  • On the menus: the stage 3 sample menu and the peritoneal dialysis menu use leached potato. Their numbers are for unleached potato, so they are on the safe side.

In the app

The app's food list has boiled potato but no leached potato. Log it as "Potato, boiled, peeled": the number is about twice what is left after leaching, so you stay on the safe side. Or add your own custom food with about 130 mg potassium per ½ cup (Logging food).

Ask your care team

  1. Do I need to leach vegetables, or is my potassium fine?
  2. How often can I have potatoes, and what portion?
  3. Which other vegetables should I leach?
  4. Can I count leached potato as a lower-potassium food in my plan?

Get help now if…

Call 911 (or your local emergency number)

Your potassium has been high and you have fainting, a very slow or irregular pulse, chest pain or sudden severe weakness, or a lab tells you your potassium is 6.5 mmol/L or more (Blood potassium; Get help now).

Sources

Not yet reviewed by a clinician. Facts and sources last checked 2026-10-06.