Understanding Your Kidney Lab Work

If you have kidney disease, you know that it can come with quite a barrage of tests and lab work.

“We drive everything we do based on lab work. That’s the gold standard,” says Dr. Richard Gibney, a nephrologist at the University of Texas Health Science Center San Antonio. “How are you doing today compared to one, three, or six months ago? Your lab work tells us what we need to do to keep you healthy.”

As valuable as lab work is, it can also be confusing and overwhelming.

“This is a large part of what I do every day,” explains Dr. Gibney. “Questions about lab work pop up again and again, and I’m happy to do what I can to educate our patients. If you can understand and focus on just a few key numbers, you can set goals with your doctor and become much more engaged in your care.”

Below, we’ve compiled a few answers to frequently asked questions about labs. With a bit of knowledge and proactivity, you too can become an integral part of your healthcare team.

Should I be worried about my lab results?

Your kidney lab work is critical, but it can also be intimidating!

“For many patients, the moment they hear about a ‘decrease in kidney function,’ their minds spiral into a dark place of worry and fear,” says Dr. Gibney. “They wonder if they are going to have to go on dialysis, get a kidney transplant, or even die.”

If this is you, be reassured that most of the time, an abnormal test result is no cause for alarm, but it should always be taken seriously. Early detection and prevention can make a big difference in preserving your health and quality of life down the line.

It’s all about trends and progress

Perhaps the most critical point about lab work is that we often look for trends and progress over time. Has your GFR dropped one or two points over the last ten years? You are probably doing just fine, but your doctors may still want to run a few tests to make sure.

If your doctors track a marked decline over weeks or months, you need to pay close attention. You will likely need to consider medicine or lifestyle change to stay healthy.

“We’re looking to stabilize kidney function wherever you are,” says Dr. Gibney.

The good news? If we can catch problems early, we now have a wealth of medicines and ways to help preserve kidney function and keep you off dialysis.

What lab tests detect kidney disease?

Your recommended lab work depends on several factors, including age, sex, and health. The first and most important lab test for kidney disease is simply detection. Kidney disease is SILENT.

According to the United States Renal Data Systems (USRDS), 92% of CKD 1-3 patients are unaware that they have kidney disease. How can we solve this monumental issue? Simply by performing routine lab work and communicating the results with the patients and provider.

Kidney disease detection starts with a standard urinalysis. This test will identify early warning signs like protein or abnormal cells in your urine.

• Urinalysis: everyone should get a urinalysis once a year

What kidney lab work tests do CKD patients need?

If a urinalysis reveals any red flags, your doctor will want to follow up with several tests to learn more about your condition.

Yet again, data reveals that the American medical system still fails to do its part in investigating kidney lab work abnormalities. According to a recent study by the National Kidney Foundation, 80% of patients with CKD do not receive appropriate testing.

If you are concerned about the results of your basic urinalysis, don’t hesitate to ask your doctor what additional tests might be needed. These more advanced tests may include:

• Complete Blood Count (CBC): tests for anemia
• Comprehensive Metabolic Profile (CMP): measures different substances in your blood that help show whether or not your kidneys are working properly
• Urine Protein to Creatinine Ratio (UP/UC): tests for protein in your urine, a warning sign of kidney issues

Based on the results of your tests, your doctor will likely want to schedule follow-up lab work down the line. For CKD patients, the frequency of your lab work depends on the progression of your disease and your unique risk factors:

• Mild issues may require lab work every six months
• Moderate issues may be every three months
• Advanced issues may be monthly

What do my kidney lab work results mean?

Once you get your lab results, you might be even more confused than before! There are various metrics and numbers related to kidney health, but we’ll try to outline a few of the most important ones here.

Once you have a better idea of what’s going on, you can have a more informed conversation with your doctor to understand your health and identify the best path forward.

Essential kidney numbers

The two most important numbers for kidney disease detection are GFR and proteinuria:

1. Glomomerial Filtration Rate (GFR): This number shows how well your kidneys work as a filter. It’s measured in cc/min. Although it’s not an exact measure of kidney function, it’s roughly equivalent. GFR is your most important marker of kidney health.
   1. Normal: A completely healthy GFR should be >90
   2. Pay attention: A mild decrease in function may not be significant and is typically a normal part of aging. Your doctor will still want to keep an eye on things to ensure there is no further decline.
   3. Red flag: A moderate to major decrease may be a call for concern. Your doctor will order further lab work to understand the issue better.
2. Proteinuria UP/UC: Any protein in your urine indicates that your kidneys may not be operating at full health. This number is measured in mg/day.
   1. Normal: There should essentially be no detectable protein in your urine.
   2. Red flag: If you have both protein in your urine and a decreased GFR, you need to start thinking about medicines and therapies to preserve kidney function.

Advanced kidney numbers

If you’re new to kidney lab work, don’t worry too much about the following information. Skip over this section and come back when you’re ready!

Once you’re ready to move on, these advanced numbers can help you further understand how your diet, lifestyle, and medications are all working together to affect your kidneys.

1. Potassium: If you have a decrease in kidney function, your body will have trouble handling potassium. Too much of it can slow down heart rate and harm your heart. Potassium comes from your diet (potatoes, bananas, citrus, chocolate, cactus), but certain drugs can also increase potassium.
   • Normal: 3.5-5.1 mmol/L
     
2. Phosphorus/Calcium: If you have a severe loss of kidney function (CKD 4-5), your body will also have trouble handling phosphorus (which is common in all sorts of foods). Phosphorus is directly tied to calcium. When phosphorus goes up, calcium goes down, which can lead to progressive bone problems.
   • To control phosphorus, you may need to take sevelamer or other “binders.”
     Normal Phosphorus: 2.8-4.5 mg/dL
   • To control calcium, you may need to take vitamin D.
     Normal Calcium: 8.5-10.5 mg/dL
     
3. Hemoglobin (HGB): Your kidneys produce a hormone called erythropoietin, which regulates red blood cells in your body. If you have CKD 4-5, you may have a decreased amount of this hormone, and your bones won’t produce as many red blood cells as they should. In this case, you can take synthetic hormone shots every 2-4 weeks that will help raise your blood count. These hormones can help you avoid blood transfusions and have a lot better energy. You may also need iron supplements for the hormones to work.
   • Normal: 14-18g/dL
     
4. CO2: A critical job of the kidneys is to keep your pH in balance. Your body is a factory, and too much base or acid can cause problems. If you have CKD 4-5, your kidneys might need help regulating your pH to preserve kidney function and keep other bodily systems healthy.
   • Normal: 21-31 mmol/L
     
5. Albumin: May reflect nutrition or proteinuria.
   • Normal: 3.2 – 5.5 g/dL

Home health data

Some of your most critical day-to-day numbers don’t require lab work or fancy tests. With the right tools and appropriate coaching and training, you can easily track your basic vitals at home. Understanding these numbers can help you manage your diet, lifestyle, and medications for optimal health.

Understanding these numbers is crucial for beginning and expert patients alike!

1. Blood pressure (BP): high blood pressure can cause stress and scarring in your kidneys. Watch your BP to help keep your kidneys healthy. Goal: Diastolic <90 (bottom number). Ideal would be  120/80
2. Blood sugar (BS): high blood sugar can also cause stress on your kidneys, but low blood sugar can be dangerous for diabetics. Watch your diet and activity to control your blood sugar, stay healthy, and feel your best. Goal: 70-110
3. Weight: sudden increase in weight can indicate water retention, often accompanied by swelling of the lower feet and legs. Talk to your doctor about your sodium intake and medications to help balance the fluid load on your kidneys.

For more information, refer to our blog about tracking your data.

We have found all our patients to be good and smart. With coaching and training, almost anyone can track their medications, BP, BS, and weight at home.

Learn more with Dr. Gibney, live on DadviceTV

Kidney disease may be SILENT, but lab work reveals a wealth of valuable information to help you and your doctors understand what’s going on inside your body. When your numbers are good, you’ll feel better today, and you’ll increase your chances of staying healthy in the future.

To learn more about kidney lab work, join the conversation with Dr. Gibney on DadviceTV via YouTube Live.

How to understand your renal labs

Wednesday, February 23, at 7 EST

Live on the DadviceTV YouTube channel