Understanding your Blood Results for Patients with Chronic Kidney Disease (CKD)

This document is designed to help you understand the various, common test results you will find in your renal clinic letters. For some results the desired range for a person with CKD is different from that of a person without CKD. If you are unsure or concerned about anything, please ask one of the renal team.

Albumin

This is the main blood protein. Low levels can be seen if the kidneys are leaking protein as part of an illness or if there is poor nutrition for whatever reason.

Bicarbonate

This is a measure of how acidic the blood is. The kidneys rid the body of waste acid that is produced as a normal bodily function. If the kidneys are not working well this acid builds up. Bicarbonate goes down when acid levels are high so if your bicarbonate level is low, we know the blood is too acidic. Acidic blood can cause problems with potassium levels (see below), worsen kidney function in the long run and is bad for bone and blood vessel health.

Corrected Calcium

This is needed for bone, heart and muscle well-being. Levels are typically low in kidney patients due to low levels of vitamin D. High levels may be associated with medication or other illnesses.

Creatinine

This is a breakdown product of muscle. We use it to measure the kidney function because the normal kidney gets rid of creatinine from the body. As a result, high levels of creatinine tend to suggest a worsening of kidney function.

Ferritin

This is a protein that measures how much iron you have stored in your body. Kidney patients need more iron than other patients to encourage normal blood production. Low levels may prompt the doctor to suggest iron treatment as tablets or as an injection.

Folic Acid

This is another B vitamin which is needed for blood production. Often deficient in dialysis patients, low levels can be treated with vitamin tablets.

Glomerular Filtration Rate (GFR)

This is your kidney function. Essentially it tells us how well your kidneys are cleaning the blood. Normal levels are over 60 and patients typically start dialysis treatment when it is less than 10. This is calculated from the creatinine measurement in your blood test. Watching how GFR changes over time can help us work out how the kidneys might be in the future. It is sometimes referred to as a percentage.

Haemoglobin (Hb)

This is the blood count. Patients with chronic kidney disease tend to become anaemic i.e. have low Hb levels. This is because the kidneys produce EPO or Erythropoietin which is a hormone that tells your bone marrow to make blood. Kidney patients tend not to do this so well and then become anaemic. Low Hb can result in feeling tired, cold and lethargic.

Parathyroid Hormone (PTH)

This protein is released in response to low calcium levels. Kidney patients will usually develop low vitamin D levels, and this tends to cause PTH to become raised. High levels tend to result in weakened bones and hardening of the arteries. High levels may prompt your doctor to suggest special vitamin D tablets. Very high levels of PTH can sometimes lead to the need for an operation to remove the overactive glands.

Phosphate

This is a salt found in food, especially dairy products and processed foods. High levels of phosphate in the blood can lead to hardening of the arteries and cause overactivity of the parathyroid glands (see PTH or parathyroid hormone) which can weaken bones. This is sometimes represented by the chemical symbol PO4.

Potassium

This is often represented by its chemical symbol K. Potassium is a salt that is important for controlling the electrical functions of the body, especially the conduction system in the heart. The kidneys remove potassium from the body so patients with kidney disease, especially if kidney function is very low, tend to get high levels. Dietary restriction of foods containing potassium and avoidance of drugs that raise it may be necessary.

Sodium

Often represented by its chemical symbol Na, this is essentially salt. Kidney disease tends to result in salt build up and with that comes fluid retention. A diet low in salt can help in the control of high blood pressure or help combat fluid retention.

Urea

This is a breakdown product of protein, produced by the liver. The kidneys get rid of urea from the body and so patients with kidney disease will often have high levels. Very high levels of urea can result in itching, sickness and generally feeling ill. Levels of over 30 might be a sign that dialysis treatment could be needed soon. This is sometimes represented by its abbreviations U or Ur.

Vitamin B12

Vitamin B12 is needed for blood production and low levels may prompt the doctor to recommend replacement injections.

This is not an exhaustive list so if you have any questions, please ask a member of staff who will be happy to explain things for you.

To find out your own specific blood test results we can offer you access to an online platform called Patient Knows Best (PKB). All you need is an email address and internet access. If this is of interest to you then please feel free to ask at you next renal clinic appointment.

Contact numbers

We hope that you have found this information useful. If you have any questions or are worried about anything, please speak to the following Dorset County Hospital staff:

East Dorset Renal Specialist Nurses team: 01202 307433

West Dorset and South Somerset Renal Specialist Nurses team: 01305 254782

About this leaflet

Author: Dr Paul Murray, Consultant Nephrologist
Written: June 2025
Approved: June 2025
Review date: June 2028
Edition: v2

If you have feedback regarding the accuracy of the information contained in this leaflet, or if you would like a list of references used to develop this leaflet, please email patientinformation.leaflets@dchft.nhs.uk