Creatinine is a byproduct of the muscle-building amino acid creatine. It's often measured in blood or urine tests to check for signs of disease — indeed, low or high creatinine levels can be a clue that you have certain health conditions. So if your creatinine is low, what does that indicate?
First things first, creatinine is a substance your body produces when your muscles break down creatine for energy, according to the Cleveland Clinic. Your kidneys then filter creatinine out of your blood and pass it out of your body through your urine, per the Mayo Clinic.
Video of the Day
Creatinine is a byproduct of muscle function, so people with more muscle tend to have more creatinine in their blood. Typically, though, normal creatinine levels for adults without underlying kidney problems and who are not pregnant range from 0.59 mg/dL to 1.35 mg/dL, per the Mayo Clinic.
But if your test result falls below these thresholds, you have low creatinine levels. And the symptoms of low creatinine vary depending on the underlying cause (more on those later).
So what does low creatinine mean, exactly? Here are the common causes of low creatinine to consider.
1. Low Muscle Mass
Remember, creatinine levels are typically higher in people with more muscle. So if your creatinine level is low, it can indicate decreased muscle bulk, according to July 2016 research in the Journal of Thoracic Disease.
Sometimes, this reduced muscle mass isn't huge cause for concern — for instance, you lose some muscle naturally as you age, according to Harvard Health Publishing. But other times, this muscle loss can be a sign of illness, so if you have low creatinine and additional symptoms, visit your doctor to determine the underlying cause.
According to the Cleveland Clinic, signs that you're losing muscle mass include:
- Loss of stamina
- Difficulty performing daily activities
- Walking slowly
- Poor balance
- Decrease in muscle size
2. Low-Protein Diet
Your diet effects your creatinine levels — specifically, not getting enough protein can lead to low creatinine, according to the University of Rochester Medical Center. So if you follow a vegetarian or vegan diet, you may be concerned about developing low creatinine.
However, you have to severely lack protein for this to affect your creatinine levels (think chronic malnourishment).
In fact, vegans' and vegetarians' creatine intake isn't typically cause for concern — most people on these meatless diets actually meet or exceed their daily protein recommendations through plant-based sources of the nutrient (like nuts, seeds and legumes), per the National Academy of Sports Medicine.
The takeaway: Eating an extremely low-protein diet in the long term can contribute to low creatinine blood test results. That said, if you follow a vegan or vegetarian diet, you likely don't have anything to worry about.
Creatine for Vegans
Not all supplemental creatine is vegan- and vegetarian-friendly. So if you're looking for creatine for vegans and vegetarians specifically, try these plant-based creatine powders instead:
Being pregnant can also make your creatinine low.
Here's what causes low creatinine when you're pregnant: During pregnancy, your kidneys more efficiently clear waste products — including creatinine — from your bloodstream, according to the Journal of Thoracic Disease research.
4. Liver Disease
Severe liver disease is another possible cause of low creatinine, according to the University of Rochester Medical Center. Your liver helps with creatine production, so when the organ isn't working well, you can develop low creatinine levels, per the Journal of Thoracic Disease research.
According to the Mayo Clinic, besides low creatinine, symptoms of liver disease include:
- Abdominal pain and swelling
- Swelling in the legs and ankles
- Itchy skin
- Dark urine
- Pale stool
- Chronic fatigue
- Loss of appetite
- Bruising easily
If you experience any of these symptoms, visit your doctor to see if an underlying liver problem is to blame.
- Cleveland Clinic: "Creatinine Clearance Test"
- Mayo Clinic: "Creatinine test"
- Journal of Thoracic Disease: "The two sides of creatinine: both as bad as each other?"
- Harvard Health Publishing: "Preserve your muscle mass"
- University of Rochester Medical Center: "Creatinine (Blood)"
- National Academy of Sports Medicine: "CAN YOU GET ENOUGH PROTEIN (AND OTHER NUTRIENTS) ON A VEGAN DIET?"
- Mayo Clinic: "Liver disease"
- Cleveland Clinic: "Sarcopenia"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.