High Creatinine Levels: Checker & Guide

High creatinine in brief

Creatinine is a waste product made at a fairly steady rate by your muscles from creatine, a compound that muscles use for energy. It passes into the blood and is removed almost entirely by the kidneys. Because the kidneys clear it so reliably, the creatinine level in the blood is the standard everyday marker of kidney filtration: when the kidneys filter less, creatinine goes up.

Key facts about high creatinine:

• A typical adult reference interval is about 0.7–1.3 mg/dL for men and 0.5–0.95 mg/dL for women (MedlinePlus), or roughly 62–115 µmol/L and 44–84 µmol/L. The NBME exam reference uses 0.6–1.2 mg/dL for adults. Your laboratory's range may differ.
• A creatinine above the range may mean reduced kidney function, but it can also come from high muscle mass, dehydration, a large cooked-meat meal, creatine supplements and some medicines that block creatinine secretion without harming the kidney.
• Creatinine on its own is a crude measure. Labs turn it into an eGFR using your age and sex, which is far more informative.
• A sudden rise from your usual value – even within the "normal" range – can signal acute kidney injury (AKI), which needs prompt assessment.

The checker above compares your creatinine with the typical range for your sex, calculates your eGFR (CKD-EPI 2021) and its GFR category, and – if you enter a previous "baseline" creatinine – applies the KDIGO criteria for acute kidney injury.

Creatinine levels chart

This table is only a rough guide. Because creatinine depends on muscle mass, the same value means different things in different people. A creatinine of 1.3 mg/dL gives an eGFR of about 67 in a 50-year-old man but about 50 in a 50-year-old woman, and about 56 in an 80-year-old man. To convert between units, multiply mg/dL by 88.4 to get µmol/L, or use the creatinine converter.

Why creatinine rises

Reduced kidney filtration

• Chronic kidney disease (CKD) – most commonly due to diabetes and high blood pressure, but also glomerulonephritis, polycystic kidney disease and other conditions. The rise is usually gradual over months to years.
• Acute kidney injury (AKI) – a sudden drop in kidney function over hours to days, often during a serious illness.

Reduced blood flow to the kidneys ("pre-renal")

• Dehydration from vomiting, diarrhoea, heat, poor intake or high fever.
• Low blood pressure, heart failure, sepsis or significant bleeding.
• Medicines that reduce kidney blood flow, such as non-steroidal anti-inflammatory drugs (NSAIDs), especially combined with diuretics and ACE inhibitors or ARBs.

Blocked urine outflow ("post-renal")

• Enlarged prostate, kidney stones, tumours or a blocked catheter. Relieving the blockage often allows creatinine to fall back.

Reasons unrelated to kidney damage

When these explanations are likely, clinicians may repeat the test after avoiding meat and exercise, or measure cystatin C, which is not affected by muscle mass or diet.

Acute kidney injury: when a rise matters most

Acute kidney injury is defined by how fast creatinine rises, not by how high it is. The KDIGO 2012 AKI guideline defines AKI as any of:

• A rise in creatinine of 0.3 mg/dL (26.5 µmol/L) or more within 48 hours, or
• A rise to 1.5 times baseline or more, known or presumed to have occurred within the prior 7 days, or
• Urine volume under 0.5 mL/kg/h for 6 hours.

It then stages AKI by severity:

The checker above applies the creatinine criteria when you enter a previous value. It cannot check timing or urine output, so a staging result means "this rise would meet the creatinine criterion if it happened within the time window".

Worked example: a usual creatinine of 0.9 mg/dL that is now 1.9 mg/dL is a ratio of 2.1 – the creatinine criterion for KDIGO stage 2, even though 1.9 might not look dramatic in isolation. A rise from 0.9 to 1.2 mg/dL (0.3 mg/dL) within 48 hours meets stage 1, while both values could appear close to normal on a report.

AKI is common in hospital, especially in people with infections, after surgery, with dehydration, or with existing CKD. Many cases recover fully when the cause is addressed, but AKI also increases the risk of future CKD, so follow-up tests are usually advised.

High creatinine and eGFR

eGFR uses creatinine, age and sex to estimate how much the kidneys filter each minute. It is reported in mL/min/1.73 m² and classified by KDIGO GFR categories:

An eGFR below 60 for more than three months is chronic kidney disease. eGFR equations assume stable kidney function, so they overestimate kidney function while creatinine is rising during AKI. The GFR levels page explains the categories and the KDIGO heat map, and the eGFR calculator shows the full calculation.

Symptoms of high creatinine

High creatinine itself does not cause symptoms. Mild-to-moderate kidney impairment usually has no symptoms at all, which is why blood tests matter. With more advanced kidney disease or AKI, people may notice:

• Reduced urine output, or passing urine more at night.
• Swelling of the ankles, feet or around the eyes.
• Tiredness, poor appetite, nausea, itching.
• Shortness of breath from fluid build-up.
• Confusion in severe cases.
• Foamy urine (from protein) or blood in the urine, depending on the cause.

What usually happens next

If your creatinine is raised, a clinician will commonly:

1. Compare it with previous results to see whether it is new or longstanding.
2. Repeat the test, often within days if the rise is new or large, or in weeks to months if it is mild and stable.
3. Check urine for albumin (UACR) and blood.
4. Review medicines, including over-the-counter painkillers and supplements.
5. Assess hydration and blood pressure.
6. Arrange a kidney ultrasound in some cases, particularly if a blockage is possible.
7. Measure cystatin C if muscle mass or diet could be distorting creatinine.

Treatment depends on the cause and is decided with your care team.

Reading creatinine with BUN

Creatinine is usually reported alongside blood urea nitrogen (BUN) or urea. Comparing the two can hint at the cause of a high creatinine:

The ratio is only a clue, but it is quick to calculate – the BUN/creatinine ratio calculator does it in US or SI units. A BMP gives you both values together with electrolytes, which can also shift when kidney function changes: potassium may rise and bicarbonate fall as filtration falls.

What about low creatinine?

A low creatinine is usually not a kidney problem. It most often reflects low muscle mass – in older adults, people who are frail or have lost weight, after amputation or with neuromuscular conditions – or pregnancy, when the kidneys filter more. Severe liver disease can lower creatinine because the liver makes creatine. The important practical point is that a low creatinine can make kidney function look better than it is: eGFR calculated from a very low creatinine may overestimate true kidney function, and cystatin C may be more reliable.

How creatinine is measured

Creatinine is measured in a standard blood sample, usually by an enzymatic method or the older Jaffe (alkaline picrate) reaction. Modern methods are standardised to a reference called isotope dilution mass spectrometry (IDMS), which is what the CKD-EPI equations assume. Some substances – ketones in diabetic ketoacidosis, high bilirubin, certain antibiotics – can interfere with the Jaffe method. A 24-hour urine collection can also be used to measure creatinine clearance directly, though it is cumbersome and prone to collection errors.

Creatinine in special groups

How to prepare for a creatinine test

• Avoid eating a large amount of cooked meat in the 12 hours before, if your clinician agrees.
• Avoid strenuous exercise the day before.
• Pause creatine supplements for several days if possible and tell your clinician you take them.
• Drink normally – being dehydrated can raise creatinine.
• Tell your clinician about medicines, including trimethoprim and anti-inflammatory painkillers.

When to see a doctor

• A new high creatinine, or a rise from your usual value – particularly a jump of 0.3 mg/dL or more, or 50% or more.
• eGFR below 60 for the first time.
• Seek urgent care if a high creatinine comes with very low urine output, vomiting and inability to drink, confusion, breathlessness or chest pain.