Kidney patients, particularly those with chronic kidney disease (CKD) who are undergoing dialysis, often need over-the-counter (OTC) vitamin supplements. CKD is characterized by a decline in kidney function and the inability of the kidneys to remove waste and excess fluid from the body. Dialysis is an artificial way of filtering and removing waste and excess fluid when the kidneys are not working properly. According to the National Kidney Foundation (NKF), CKD changes an individual's vitamin requirements. Dialysis can also increase vitamin losses, and food restrictions associated with kidney disease may decrease dietary intake of certain vitamins.
Vitamin D
Vitamin D is a fat-soluble vitamin that is produced by the body when exposed to sunlight. It is also in foods like milk and fortified cereals and grains. Vitamin D functions with calcium to build and strengthen bones and teeth. According to the NKF and Nephron Information Center (NIC), CKD is associated with low levels of vitamin D, because vitamin D is synthesized in the kidneys. The Mayo Clinic says vitamin D and calcium supplements are often given to CKD patients to prevent weak and brittle bones.
The recommended dietary allowance (RDA) for vitamin D for adults is 5 to 10 micrograms per day; however the NIC says the recommended amount of supplemental vitamin D for a CKD patient needs to be determined on an individual basis by a physician. According to the Office of Dietary Supplements (ODS), vitamin D can be toxic in high doses and cause nausea, vomiting, poor appetite, constipation, weakness and weight loss. OTC vitamin D supplements should be taken according to the manufacturer's dosing directions while being monitored by a physician.
B Vitamins
B vitamins include thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, folate and vitamin B12. B vitamins help convert food into usable energy through a process called metabolism. According to the NIC, people with CKD are often deficient in B vitamins, because B vitamins are found in foods that are often restricted in diets for kidney patients.
The NKF says B vitamins are often grouped together and supplemented as a B-complex vitamin. The NIC notes that people on dialysis have a particular need for folic acid, B6 and B12. They recommend that dialysis patients take 800 micrograms to 1 milligram of folic acid and 10 milligrams of B6 a day. B vitamins have a low risk of toxicity because excess amounts are usually excreted in the urine, however patients taking OTC B vitamins should follow dosing recommendations by the manufacturer or a physician.
Vitamin C
People with CKD may be deficient in vitamin C due to dietary restrictions. According to the NKF, vitamin C is often supplemented in CKD because it keeps tissues healthy and can help prevent infections. The NIC warns that no more than 60 milligrams of vitamin C a day should be taken by kidney patients. Vitamin C in high doses can combine with a compound called oxalate to form oxalate crystals. Oxalate crystals can build up in the bones and muscles and cause arthritis, muscle weakness and impaired muscle function.
