The amount of potassium and phosphorus in fish varies depending upon the type of fish (see the chart below). The amount of potassium and phosphorus you can have each day will depend on your stage of kidney disease and/or the type of dialysis you receive.
Chronic kidney disease (CKD) and transplant
Most people with kidney disease or transplants do not have to limit fish.
When you reach the later stages of kidney disease your doctor may want you to limit the amount of protein you eat. Eating fish can still be a great option but you might need to eat smaller portions. Talk to your doctor or to a kidney dietitian to find out your individual needs.
With a transplant, you will want to avoid raw or undercooked fish as it can pose an increased risk of foodborne illness (also known as food poisoning). Transplant patients are at higher risk since they take immunosuppressive medications or “anti-rejection medications” to protect the new transplanted kidney.
Hemodialysis (3 times a week) and daily home or nocturnal hemodialysis/peritoneal dialysis
People on dialysis have increased protein needs. Include fish two times per week as a great lean protein option and a way to help boost intake of omega-3 fatty acids. The potassium and phosphorus content of fish varies (see the chart below). Choose fresh fish when possible because it is lower in sodium. Canned fish can be high in sodium. Always talk to your kidney dietitian to find out how you can include fish in your diet.
Eating fish will not have an effect on forming kidney stones.
Larger fish like tuna and sharks may have high mercury concentrations. See list of seafood, mercury levels and maximum serving recommendations per week at https://www.verified.org/articles/guides/mercury-poisoning-from-fish.