The urine creatinine 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, urine creatinine levels can be used as a measure of kidney health [3, 1, 4].
If kidney function is impaired, creatinine levels in urine decrease.
Creatinine Urine Test
Why Doctors Order It
Doctors can order a urine creatinine test to [5]:
- 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
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 can be used to monitor kidney disease development and recovery [6].
Urine Test Types & Procedure
There are two main types of urine creatinine 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].
24h Urine Creatinine 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.
Urine Creatinine Normal Range
Regular (Random) Test
Urine creatinine test results are usually reported in mg/dL (milligrams per deciliter).
The normal range is around 20 – 275 mg/dL in women and 20 – 320 mg/dL in men. Ranges may vary between laboratories.
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. Ranges may again vary slightly between laboratories doing the testing.
Low Urine Creatinine
Causes
Causes shown here have been associated with low creatinine levels. Work with your doctor or another health care professional to get an accurate diagnosis. Your doctor will interpret your value, taking into account your medical history, symptoms, and other test results.
Low urine creatinine levels can be caused by
- Kidney damage and disease [7, 8]
- Overhydration (when your urine is very diluted) [7]
- Muscle wasting (in illness or aging) [9, 10, 5, 11]
- Diabetes [8]
Some drugs can also decrease urine creatinine levels [12]:
- Antibiotics such as trimethoprim/sulfamethoxazole (Bactrim, Cotrim, Septra)
- Histamine H2 receptor blockers that inhibit stomach acid production: cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac) [12]
- NSAIDs such as indomethacin (Indocid, Indocin) and ibuprofen [12, 13]
- Acetaminophen (Tylenol, Panadol, paracetamol) [14]
Increasing Creatinine
The most important thing is to work with your doctor to find out what’s causing your low urine creatinine and to treat any underlying conditions.
If you are suffering from kidney disease, you may need to 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 [15, 16].
Read this post about the renal diet to find out which foods to eat and avoid if you have kidney disease.
High Urine Creatinine
Causes
Urine creatinine levels correspond to lean body mass and can be higher if your muscle mass is above average. Your doctor will interpret your value, taking into account your medical history, symptoms, and other test results.
Causes shown here have been associated with high creatinine levels. Work with your doctor or another health care professional to get an accurate diagnosis.
High levels of creatinine in urine can be due to:
- Dehydration [5]
- Strenuous exercise [17, 1]
- Diet high in meat and protein [17, 5]
- Creatine supplements [17]
- Pregnancy [18, 19]
- Early diabetes [18, 20, 19]
- High blood pressure [19]
- Obesity [18, 19]
- Polycystic kidney disease [18]
- Sickle cell anemia [18, 19]
Lowering Creatinine
The most important thing is to work with your doctor to find out what’s causing your high urine creatinine and to treat any underlying conditions.
In addition, make sure you are well hydrated as you are taking the test and in general [5].
Takeaway
Your urine creatinine 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 issues. Muscle-wasting disease and certain medications can also lower creatinine in the urine. Higher urine creatinine levels can be due to having more muscle mass than average, a diet high in meat and protein, pregnancy, obesity, early diabetes and some other conditions. Dehydration can also raise urine creatinine, so make sure you are getting enough fluids. If your levels are abnormal, work with your doctor to find out what’s causing that and to treat any underlying conditions.
Learn More
The following markers are also used to check kidney health:
