Lab results are very important to monitor how your kidneys are functioning and side effects of kidney disease. Lab results will help your doctor and medical team figure out the best treatment for you.
Here are some of the most important lab tests to know for kidney health. Use this guide to help you understand what some of those numbers mean!
Blood Tests
Creatinine (normal range: 70 – 120 μmol/L for men and 50 – 90 μmol/L for women)
Creatinine is a waste product from your muscles. As with most waste products, it is your kidney’s job to get rid of creatinine. When your kidneys are not working properly, creatinine builds up in your body. So, creatinine is used as a marker for how well your kidneys are working. A high creatinine level usually means your kidneys are not working as well as they should.
GFR (Glomerular Filtration Rate) (normal range: more than 90 mL/min)
GFR is a calculation to figure out how well your kidneys are working. Think of GFR as the percent of how well your kidneys are functioning compared to normal. If your GFR is 30 mL/min, your kidneys are working at 30% capacity.
GFR is classified into stages of kidney disease:
- Normal kidney function: GFR 90 mL/min or higher
- Mild reduced kidney function: GFR 60-89 mL/min
- Moderately reduced kidney function: 30-59 mL/min
- Severely reduced kidney function: 15-29 mL/min
- Kidney failure: GFR less than 15 mL/min
Sodium (normal range: 135-1495 mmol/L)
The amount of sodium in your blood helps your doctor understand how much water is in your body. Too much sodium in your blood usually means you are dehydrated. Too little sodium usually means your body is not getting rid of water like it should. The amount of sodium in your blood is not necessarily a measure of how much sodium you are eating. The amount of sodium in your blood does not change based on how much sodium you eat.
Potassium (normal range: 3.5-5.0 mmol/L)
Potassium is a mineral that our body needs to work properly. Kidneys are responsible for getting rid of extra potassium in urine. When kidneys are not working as well as they should, potassium levels get too high. High levels of potassium can cause muscle cramping and cause your heart to beat irregularly.
If your potassium is high, your doctor might change your medication. Or, they might ask you to cut back how much potassium you are eating.
Phosphorus (normal range: 0.80 – 1.50 mmol/L)
Phosphorus is another mineral our bodies need to work. When the kidneys are not able to get rid of phosphorus, phosphorus levels can get too high. Too much phosphorus in your body can cause heart disease, stroke, and weak bones.
If your phosphorus is high, your doctor might ask you to take a medication to stop phosphorus from your food from getting absorbed. They might also ask you to cut back on how much phosphorus you eat.
CO2 or Carbon Dioxide (normal range: varies by laboratory)
Carbon dioxide levels help doctors understand how much acid is in your body. A low carbon dioxide means that there is too much acid in your body. Because kidneys are responsible for getting rid of extra acid, acid levels can get too high when kidneys are not working well.
If your carbon dioxide level is high, your doctor might put you on a medication to lower it. Eating more fruits and vegetables and eating less protein can also help control acid levels in your body.
CBC Panel (Complete Blood Count) and Iron
Anemia is a condition in which you do not have enough healthy red blood cells to carry the right amount of oxygen to your body’s tissues. This is a common side effect of kidney disease. Your kidneys are important for making red blood cells, which carry iron and oxygen around your body. Your doctor may check your iron level and a complete blood count (CBC) to test for anemia. A CBC includes many labs such as hematocrit, hemoglobin, and a red blood cell count. Anemia is caused by very low red blood cells. If anemia is found, your doctor might check for other causes like low vitamin B12 or low folate levels.
Parathyroid Hormone (PTH)
Parathyroid hormone (PTH) is important for bone health and to keep the amount of calcium in your blood in a healthy range. PTH can get high in people with kidney disease. High PTH levels can cause heart disease and weak bones.
Urine Test
Protein
There should not be protein in your urine. But when kidneys are not filtering your blood like they should, protein can leak into urine. Your doctor will check to see how much protein is in your urine to figure out how well your kidneys are working.
If you have diabetes, here are some additional tests your doctor might order. Managing or preventing diabetes is an important part of kidney health!