The creatinine urine test can reveal a lot about the health of your kidneys. If you have kidney disease, your levels will be low. On the other hand, exercising often, being muscular, and eating a meat-heavy diet can increase creatinine. Read on to understand how this test works and how to interpret your results.

What is Creatinine?

Creatinine is a waste product created from the normal wear and tear of muscles. It is produced from creatine, a protein needed to generate the energy for muscle contractions [1, 2].

Its production essentially reflects lean body mass, and because this mass changes little from day to day, the production rate is fairly constant. Women, children, and older people tend to have lower levels of creatinine compared to adult men because they have less muscle mass [1].

Creatinine is removed from the body by the kidneys, which filter almost all of it from the blood into the urine. Thus, your urine creatinine levels are a good measure of your kidney health [3, 1, 4].

If your kidney function is impaired, creatinine levels in your urine decrease.

Creatinine is a waste product of your muscles that your kidneys need to flush. Poor kidney health lowers creatinine urine levels.

Creatinine Urine Test

Is it Better to Test Creatinine in the Urine or Blood?

While blood creatinine is more reliable, changes in urine creatinine happen faster. That’s why it’s a good marker to monitor for kidney disease development and recovery [5].

On the other hand, your doctor may order the creatinine blood test as a part of your basic metabolic panel (BMP) or your comprehensive metabolic panel (CMP). These tests have the advantage of giving your doctor a more complete picture of your overall health, beyond kidney function.

Urine creatinine levels better reflect quick changes in your kidney function. Urine tests are preferred over blood tests for monitoring kidney disease.

Urine Test Types & Procedure

There are two main types of creatinine urine tests:

  • Random (spot) urine test, which is when you collect a urine sample at a random time in the day and bring it to the lab for analysis
  • 24h creatinine test, which involves storing your urine into a special container over a full 24-hour period before bringing it to the lab

24h creatinine is preferred to random (spot) creatinine because it’s more accurate. However, it’s also more demanding and requires you to carefully store your urine over a 24 hour period [1].

The 24h creatinine urine test is more accurate than the random (spot) urine test.

24h Creatinine Urine Test Procedure

For the 24h test, you will initially get one or more containers for collecting and storing your urine.

You’ll only need to skip collecting your first morning urine – for example, at 9 AM. Flush this urine and note the time. That’s when your “timer” starts. Alternatively, your doctor may specify the exact time you should start collecting.

Collect the next urine into the container. Keep your container in a cold place such as the refrigerator or in a cooler on ice.

Keep collecting all your urine over the next 24 hours. In our scenario, that would be when you urinate around 8.40-9 AM the next day. The goal is to try to urinate as close as possible to the end of the 24 hour window. If you could urinate at 8.59, that would be ideal. If not, that’s still ok.

Do not collect urine after 24 hours are up! Following our example, if you collected urine at 10.10 AM, your results would be off.

Once you have collected your 24h urine, bring it to the lab for analysis as soon as possible.

It’s important to collect all urine within this time frame. If anything went wrong – you forgot to collect urine at any point, you spilled some, or you didn’t keep it in a cold place – let your doctor know. Otherwise, you risk getting inaccurate results.

Carefully follow the instructions for collecting and storing your 24h urine. Any mistakes can lead to inaccurate results.

Why Doctors Order It

Urine creatinine test can be used to [6]:

  • Check whether your kidneys are working well
  • Check if a treatment for kidney disease is working
  • Adjust the urinary levels of other markers, such as metabolites or toxins

Urine Creatinine Normal Range

Regular (Random) Test

Creatinine urine test results are usually reported in mg/dL (milligrams per deciliter).

The normal range is 20 – 275 mg/dL.

Values above 275 mg/dL are considered high, and values below 20 mg/dL are considered low.

If your levels are within the normal range, your kidneys function well and are able to remove toxins efficiently! This also means you have a lower risk of all-cause mortality [7].

24h Creatinine

Results of the 24h creatinine test are typically reported in g/24h (grams of creatinine in the urine over 24 hours).

The normal range is 0.5-2.15 g/24h.

Values under 0.49 g/24h are considered low and any value above 2.16 g/24h is viewed as high.

High Urine Creatinine

Causes

Urine creatinine levels correspond to lean body mass and can be higher if your muscle mass is above average.

High levels can also be due to:

  • Dehydration [6]
  • Strenuous exercise [8, 1]
  • Diet high in red meat (animal protein) [8, 6]
  • Creatine supplements [8]
People who have more lean muscle, eat a diet high in red meat, don’t drink enough fluids, or engage in strenuous exercise are more likely to have high urine creatinine.

How to Lower

Increase fluid intake, try to drink at least two liters of water a day! High urine creatinine may be a sign of dehydration [6].

Lose some weight if overweight. Weight loss can increase your kidney health and decrease creatinine levels [9].

To lower your urine creatinine levels, make sure to keep hydrated and lose extra weight.

Low Urine Creatinine

Causes & Health Risks

Low urine creatinine levels can be caused by

  • Over-hydration (when your urine is very diluted) [10]
  • Muscle wasting (in illness or aging) [11, 12, 6, 13]
  • Diabetes [14]
  • Chronic kidney disease [10, 14]

Some drugs also decrease urine creatinine levels [15]:

  • Antibiotics such as trimethoprim/sulfamethoxazole (Bactrim, Cotrim, Septra)
  • Histamine H2 receptor blockers that inhibit stomach acid production: cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac) [15]
  • NSAIDs such as indomethacin (Indocid, Indocin) and ibuprofen [15, 16]
  • Acetaminophen (Tylenol, Panadol, paracetamol) [17]

Low creatinine increases your risk of:

  • Frailty [18]
  • Heart disease [19]
  • All-cause mortality and in-hospital mortality [19, 20, 21]
Aside from kidney disease, other factors like illness, aging, diabetes, and certain prescription drugs can lower your creatinine urine levels.

How to Increase Levels Naturally

Low creatinine can signal low muscle mass, malnourishment, and muscle wasting. If that’s your case:

  • Adjust your diet! Make sure you are well-nourished and your diet contains enough protein.
  • Increase physical activity – exercise increases creatinine levels and it helps build muscle [22, 23].

Supplements that can help (only if your kidney function is good) include:

If you don’t have kidney problems, make sure to get enough protein and exercise to raise your creatinine urine levels. Creatine supplements might also help.

However, if you are suffering from kidney disease, you should avoid creatine, lower your protein intake, and increase dietary fiber. Kidneys must work harder when there’s more protein in the diet, which can worsen their function. On the other hand, fiber-rich foods like fruits, veggies, whole grains, and legumes improve kidney health [24, 25].

Read this post about the renal diet to find out which foods to eat and avoid if you have kidney disease.

Supplements that improve kidney health include:

If low creatinine is caused by an underlying disease, seek medical treatment.

If you have kidney disease and low creatinine, reduce protein in your diet, avoid creatine supplements, and increase your intake of fiber and kidney-protective herbs.

More About Creatinine & Kidney Function Tests

All the following markers are also important for your kidney health:

Irregular Creatinine Urine Levels?

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Takeaway

Your creatinine urine levels can reveal kidney problems.

Your doctor will either order a spot test – when you give a small urine sample at a random time in the day – or a 24h creatinine urine test. The 24h test is more accurate, as long as you carefully follow the instructions.

If your levels are low, you may have kidney disease. Muscle-wasting disease and certain medications can also lower creatinine in the urine.

If you have low urine creatinine and kidney disease, you should reduce protein and increase fiber in your diet. Supplementing with kidney-protective nutrients or herbs like alpha-lipoic acid and astragalus might help as well.

If your kidneys are healthy, the amount of creatinine in your urine increases with your muscle mass. People with more muscle who engage in intense exercise and eat a lot of red meat tend to have higher levels. Dehydration can also raise urine creatinine, so make sure you are getting enough fluids.

About the Author

Mathew Eng, PharmD

PharmD

Mathew received his PharmD from the University of Hawaii and an undergraduate degree in Biology from the University of Washington.

Mathew is a licensed pharmacist with clinical experience in oncology, infectious disease, and diabetes management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions.

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