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.
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 .
If kidney function is impaired, creatinine levels in urine decrease.
Doctors can order a urine creatinine test to :
- 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
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 .
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 .
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 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.
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.
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) 
- Muscle wasting (in illness or aging) [9, 10, 5, 11]
- Diabetes 
Some drugs can also decrease urine creatinine levels :
- Antibiotics such as trimethoprim/sulfamethoxazole (Bactrim, Cotrim, Septra)
- Histamine H2 receptor blockers that inhibit stomach acid production: cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac) 
- NSAIDs such as indomethacin (Indocid, Indocin) and ibuprofen [12, 13]
- Acetaminophen (Tylenol, Panadol, paracetamol) 
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.
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 
- Strenuous exercise [17, 1]
- Diet high in meat and protein [17, 5]
- Creatine supplements 
- Pregnancy [18, 19]
- Early diabetes [18, 20, 19]
- High blood pressure 
- Obesity [18, 19]
- Polycystic kidney disease 
- Sickle cell anemia [18, 19]
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 .
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.
The following markers are also used to check kidney health:
- Creatinine Blood Levels
- BUN/Creatinine Ratio: High & Low Levels + Normal Range
- Blood Urea Nitrogen (BUN) & Hidden Causes of High or Low BUN
- Urea Test: High & Low Levels + Normal Range
- eGFR (Glomerular Filtration Rate) Test + How To Increase It
- Cystatin C Test Levels, Normal Range + How to Lower it