One of the blood tests your physician will order when you have kidney disease is a renal function panel. This test, and other labs for further health assessment, will be reviewed by your ordering doctor. Your labs can provide us with a lot of details of what is going on inside your body- whether you realize it or not. Let’s dive in to exactly what a renal function panel includes, as well as other tests you may have.
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About lab results
Keep in mind that lab results are a “snapshot” of what is happening at the time of your blood draw.
Your labs will change from result to result. It’s important to know that just one result that is out of range may not tell much. Getting retested is important to confirm problems. Track the patterns and changes to get a better feel for how your body and kidneys are doing. If you have results out of the normal/reference ranges, your physician will likely order follow-up labs for confirmation and diagnosis.
Be active in your own healthcare!
Review your results and ask as many questions as needed for you to feel comfortable with your results. You may or may not have all of these labs in your results – your physician will determine which labs are necessary. Dietitians help physicians in providing further explanation of nutrition-related labs and how your diet can impact your health. Here is a breakdown of some kidney-relevant labs for you to keep in mind.
Renal Function Panel
If you have told your doctor about a family history of kidney disease, or you are already aware of your own diagnosis of kidney disease, you are likely to have a renal panel or renal function panel in your blood test results.
These results can be drawn anywhere from monthly to annually (once per year). The timing will be based on your nephrologist or physician’s orders. Many doctors are open to having additional labs drawn when requested – but be prepared to put in work if you want to get your renal function panel drawn more frequently.
Glomerular Filtration Rate
The glomerular filtration rate, or GFR, is a measurement of your kidney function of blood filtration. This is a calculation based on your gender, age, size, and creatinine in your blood. This is one of the most common tests to assess your kidney function.
A normal GFR is above 90. Some lab reports will look for GFR of at least 60, as function will naturally decline as we age.
GFR is associated with stages of kidney disease. Kidney failure is associated with a GFR below 15. Not just one low value will suggest kidney disease.
A low GFR for three months can indicate kidney disease along with diagnosis from a physician. Calculate your eGFR here.
Blood Urea Nitrogen
Blood urea nitrogen – otherwise known as urea nitrogen or BUN – is a measurement of protein breakdown in the body.
BUN is generally below 20 mg/dL but will often rise when there is kidney damage. This is because the kidneys are unable to keep up with eliminating excessive waste.
BUN may trend upwards of 80 mg/dL when on dialysis.
A lower-protein diet can help in reducing BUN but if done improperly can increase the risk of protein-energy wasting and malnutrition, which can then increase inflammation and potentially increase kidney damage.
Creatinine is a waste product from normal muscle metabolism and breakdown. It is not directly related to dietary protein intakes.
A normal serum creatinine level is between 0.84 – 1.21 mg/dL in the blood test but can vary for many reasons, including gender, age, and activity level.
With chronic kidney disease, creatinine will increase as kidney function decreases. This is because the kidneys begin to struggle with eliminating waste from the body. Creatinine levels measured in chronic kidney disease can range anywhere from 2.0-15.0 mg/dL depending on stage and other health conditions.
One study found that eating meat prior to a blood draw for creatinine testing, creatinine was falsely higher.
While creatinine is not directly related to nutrition, by finding other culprits that impact your kidney health may help to lower or stabilize creatinine levels. This can come from dietary changes that help promote a healthy kidney!
Your serum albumin is protein and measurement of inflammation. Old-school thought was that albumin would tell us how much protein you are eating when we now know that it is much more than just that.
A normal albumin will range from about 3.4 – 5.0 g/dL. As it can signal problems with inflammation, it will decrease when there is more inflammation.
If you’ve been hospitalized and have access to your labs, take a look at your albumin before, during, and after your hospitalization. When we are hospitalized, we go through a lot that can be inflammatory. Once we get better, our albumin can increase and show we are healing.
Sodium is the most common particle in our blood outside of our cells. It helps with muscle function, acid-base balance, cellular balance and osmotic pressure of body fluids.
Serum sodium is part of your comprehensive metabolic panel, basic metabolic panel, or renal panel. While many associate this with the amount of salt you eat, it is much more than just that.
Your blood test result is not a reliable measurement of your sodium intake. It is a better marker for your fluid balance.
The blood serum sodium levels are typically between 135 – 145 mEq/L in your blood test results. If you experience edema, or swelling of extremities with excessive fluids, you may see a slightly lower sodium level. A sodium level above the normal range can be a sign of dehydration.
It may also be falsely low if you drink a lot of water right before your blood draw!
It’s been though before that if your sodium is out of range that you should eat more/less salt. That may not necessarily be the case and may cause more issues. Before making drastic changes in your diet, it’s best to consult with a registered dietitian to help assess all factors that may be causing an out-of-range sodium level.
Calcium is the number one mineral stored in our body. Calcium helps with many things including bone health and muscle contraction. General calcium levels are between 8.5 – 10.2 mg/dL.
As our kidneys help regulate our bone health, calcium becomes an important value to monitor with kidney disease.
With many people with CKD, calcium can trend out of range. Calcium can either go above the healthy range or below. This often leads to either including or avoiding calcium supplements, depending on your labs and other health conditions.
Never take calcium supplements without first discussing with your nephrologist. Excessive calcium can lead to calcification in your soft tissues, which can then lead to increased risk of heart attack and stroke.
Phosphorus is another mineral found in our body. It’s actually the second highest in quantity, behind calcium.
Phosphorus does plenty of things to help keep us healthy, such as manage how your body uses energy, build strong bones and teeth, regulate vitamin use, and help with muscle contraction (including our heart!).
Blood serum levels of phosphorus should generally be approximately 2.5 – 4.5 mg/dL, but ranges may differ depending on the individual. Some nephrology clinics have different ranges to accommodate for the expected higher ranges of phosphorus in late-stage CKD, which may look closer to 3.0-5.0 mg/dL.
Even though there is some “forgiveness” with slightly higher phosphorus levels, the Kidney Disease International Outcomes Guidelines (KDIGO) still express the need to focus on striving for a phosphorus within normal range to prevent increased risk of death.
Working with a dietitian can help assess current diet habits and identify the top phosphorus culprits in your diet.
Potassium is the third most abundant mineral in our bodies.
Potassium acts as an electrolyte and helps with nerve conductivity, muscle contraction, and fluid balance. Potassium level is generally between 3.5 – 5.0 mEq/L.
High- and low-potassium values should be reviewed quickly with your physician and healthcare team as potassium plays an important role with our hearts. A dietitian can help by reviewing your diet to balance your potassium level.
Your serum bicarbonate (aka carbon dioxide or CO2) is related to the acid-base balance, or pH levels, of your body. With kidney issues, the bicarbonate levels tend to decline. The body then leans towards a more acidic state. Normal bicarbonate levels in the blood are approximately 20 – 29 mEq/L.
As bicarbonate declines, you may find that your doctor prescribes sodium bicarbonate tabs or, in some cases, baking soda. However, by paying attention to the potential renal acid load in your diet, you may be able to manage with some diet changes!
Please keep in mind taking baking soda or sodium bicarbonate without medical supervision is not recommended and may be harmful to your kidneys and your health.
The parathyroid hormone (PTH) levels are measured because the kidneys directly tell the body how much of the hormone is needed. PTH is responsible for balancing the calcium and phosphorus levels in our blood and body.
A normal intact PTH (or iPTH) level is between 10 – 65 pg/mL.
When the kidneys aren’t working well, this number tends to increase. This can lead to up to ten times as high as the normal range. This increase is expected in kidney disease and while it may not return to the normal range, should be monitored and stabilized.
Vitamin D is obtained from the sun and our diet and activated by our kidneys.
Normal vitamin D levels are at least above 30 ng/mL.
When kidneys aren’t working as well, vitamin D levels tend to decline. Many people with kidney disease supplement with vitamin D.
Appropriate dosing is very important as it is also unhealthy to have excessively high vitamin D levels in the body. Always consult with your nephrologist and renal dietitian about the amount of vitamin D you should be taking.
An additional consideration when supplementing with vitamin D is to make sure it’s the right type of vitamin D. I recommend vitamin D3 with vitamin K2 included to help support not only the absorption of vitamin D and calcium, but also making sure it goes to the right place.
Beyond the Renal Function Panel: Other lab tests to consider
This is a lab result associated with diabetes. Since diabetes is the number one cause of chronic kidney disease, it is common to also have a hemoglobin A1c test as well.
A HgbA1c result measures the average blood sugars you have experienced over the past 2-3 months.
Because it measures over a long period of time, it’s not typically measured more often than every 3 months.
The goal for those with diabetes is to maintain a HgbA1c at or below 7.0%.
The renal diabetic diet can seem complicated, but a very effective way of managing both diabetes and kidney disease. With diet, lifestyle, and medication changes, you can work to control your blood sugars and keep a controlled HgbA1c. This can then help keep your kidneys happy and healthy!
In addition to your renal function panel, your nephrologist or physician may also check your urine. Since the kidneys are responsible for urine production for waste removal, this can tell us a lot about what is going on with kidney function and capabilities.
This test is performed with a urine sample. It will assess if you are leaking protein (albumin) through your urine, a sign of kidney damage.
Healthy kidneys keep albumin in the blood and allows creatinine, a waste product, to pass into the urine. With kidney damage, more albumin can end up leaking into the urine which will then increase the albumin-creatinine ration (ACR) because albumin detected is increased.
Generally, a result less than 30 mg/g will indicate normal kidney function. If your ACR is between 30-300 mg/g for at least three months, it may indicate kidney damage. Above 300 mg/g suggests a lot of protein is leaking at a faster rate.
As kidney disease is also strongly associated with cardiovascular disease, it is likely that your doctor will also have a lipid panel drawn as well. This can help in assessing your cardiovascular health and identify other areas that can be focused on to help keep your kidneys healthy.
This is a measurement of the fat in your blood. Too much cholesterol can clog your arteries and increase risk of heart attack and stroke. It can also clog the blood vessels and arteries to your kidneys, which is why it’s important to know and track.
Total cholesterol should be under 200 mg/dL.
Triglycerides are a type of fat in the blood. It can accumulate due to genetics as well a dietary and lifestyle factors. Normal triglyceride levels should be under 150 mg/dL.
High-density Lipoprotein, or HDL, cholesterol is considered the “good” cholesterol. It helps by removing bad cholesterol and fats out of your arteries to keep the road clear.
A normal HDL should at or above 40 mg/dL.
This is considered the “bad” cholesterol that can contribute to heart disease and cardiovascular issues. A normal LDL should be below 100 mg/dL.
If you have kidney issues, you’ll want to discuss with your nephrologist what renal function panel labs should be tracked and how often they should be checked. This can include a basic or comprehensive metabolic panel, urinalysis, lipid panel and even a complete blood count.
Be sure you address all questions about your labs and lab results with your nephrologist or physician.
Our kidneys do a lot for us. This means there can be a lot of lab tests to reflect what is happening with our kidneys.
Keep in mind that this is not an “all-Inclusive” list of labs to track. Your doctor may want additional testing done to assess other areas that need to be monitored. This is good! Feedback is always helpful and can provide more insight.
Everyone is different and may need different testing. It’s important to have open discussions with your doctor to best understand your tests and the results.
Want some help in tracking your renal function panel?
I’ve created a one-page lab tracker that you can use to help monitor some of these labs, as well as others that may come up in your healthcare.