Blood and lab tests
What Is Creatinine on a Blood Test?
Creatinine · say it: kree-AT-ih-neenAlso written: serum creatinine, Cr, Creat
Short answer
Creatinine is a waste product from normal muscle activity that the kidneys filter out, so its blood level helps show how well the kidneys work.
What it means
Your muscles produce creatinine all the time as part of normal energy use. It passes into the blood, and healthy kidneys remove it into the urine at a fairly steady rate.
If the kidneys filter less well, creatinine can build up in the blood. That is why a creatinine test is one of the most common ways to check kidney function, and it is used to calculate eGFR.
Creatinine also depends on how much muscle a person has, recent intense exercise, eating a lot of cooked meat, hydration and some medicines. A result is best understood in context and compared with earlier results.
Where you may see it
- Kidney function tests
- Basic or comprehensive metabolic panels
- Urine tests, where it is used to correct other measurements
📄 How it looks on a report
Creatinine 1.1 mg/dL (range printed by lab)
🙅 What it does not mean
- A higher creatinine does not automatically mean kidney damage; dehydration, muscle mass or a large meat meal can raise it.
- A low creatinine is not usually a sign of better kidneys; it often reflects lower muscle mass.
- Creatinine alone does not tell the whole story. Doctors often look at eGFR, urine tests and trends over time.
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Creatinine”
Paste or upload the report and every line of it is explained, with personal details removed first.
💊 Medicines whose labels mention “Creatinine”
Plain-English explanations of each medicine, from its official FDA label.
- Ciprofloxacin
a fluoroquinolone antibacterial medicine
- Furosemide
A loop diuretic, a type of medicine that helps the body get rid of extra fluid through urine
- Levofloxacin
an antibiotic of the fluoroquinolone type
- Metronidazole
An antimicrobial medicine of the nitroimidazole type, used to treat certain bacterial and parasitic infections
🔗 Read more from trusted sources
- “Creatinine” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “creatinine”
- MedlinePlus lab test guides ↗
US National Library of Medicine
Seeing this word on your own report? Get every line of it explained, free.
Explain my report🧩 Related words
🔎 Look up another word
More words: blood and lab tests
General information about a medical word, not advice about your own results. Ask the clinician who ordered the test what it means for you.