Kidney Diet Tips

Your kidneys and vitamin D: How does it work?

istock_000007178194sunshineVitamin D is a hot topic.  Articles appear almost weekly in newspapers, magazines, journals and online.  I’ve heard several television reports just over the past week.  In a posting back in April, I covered some basics on vitamin D and why it’s important for chronic kidney disease and dialysis patients. Today I’m focusing on the best way to get vitamin D and how it works in the body.

Roll up your sleeves, omit the sunscreen and sit in the sun for 15 to 20 minutes between 10 am and 1 pm.  That’s the best and easiest way to get the vitamin D.  Amazingly, you can get as much as 10,000 IU of vitamin D if you are fair-skinned.  If you have dark pigmented skin additional time is required for the same effect.

How does this work?  When ultraviolet B rays from the sun hit your skin, vitamin D precursors stored in skin are activated and released into the blood. This form of vitamin D, 25-hydroxy vitamin D,  then goes to the liver for another activation step and finally to the kidneys for a final activation. The liver can store vitamin D until it is needed by the body.

If you have kidney disease, less vitamin D is activated, especially in advances stages of CKD and end stage renal disease (ESRD). You may want to ask you doctor to check your vitamin D level to determine if you have a deficiency.  The biologically active form of vitamin D is 25-hydroxy Vitamin D.  Normal blood levels are 40-60 ng/dl. U.S. studies show as many as 70% of the population has levels lower than this amount.  The lowest levels were found in the elderly, females, overweight and obese persons, and those with kidney disease or diabetes.

If low levels are discovered your doctor may prescribe high dose supplements for 6 to 12 weeks, followed by a daily maintenance dose of 400 to 1000 IU.  In addition to or instead of this supplement, dialysis patients and CKC patients in later stages may be prescribed a special activated vitamin D supplement.  This form of vitamin D is equivalent to the vitamin D activated by kidneys, and acts as a replacement if you have kidney disease.  Doctors monitor the effects of this special prescription activated vitamin D by checking blood calcium, phosphorus and parathyroid hormone (PTH) levels.

For more information on vitamin D and kidneys, read Vitamin D and chronic kidney disease on

Kidney diet resources from

Review and rate recipes

Discussion Forums

Monthly Recipe Alerts

DaVita Diet Helper

Sara Colman, RDN, CDCES

Sara Colman, RDN, CDCES

Sara is a renal dietitian with over 30 years experience working with people with diabetes and kidney disease. She is co-author of the popular kidney cookbook "Cooking for David: A Culinary Dialysis Cookbook". Sara is the Manager of Kidney Care Nutrition for DaVita. She analyzes recipes and creates content, resources and tools for the kidney community. In her spare time Sara loves to spend time with her young grandson, including fun times together in her kitchen.