Almost every routine blood panel ordered in Ottawa includes a line that reads "eGFR" next to your creatinine, and it is one of the most searched results on a lab report. It is also one of the most misread. This guide explains what the estimated glomerular filtration rate is, how Ontario labs calculate it, what the categories mean, and why one number below 60 is not the same as kidney disease.
What eGFR measures
Your kidneys filter waste out of your blood through millions of tiny filters called glomeruli. The glomerular filtration rate is the volume of blood they clean each minute; a healthy young adult filters roughly 100 millilitres or more per minute. Measuring that directly is impractical, so laboratories estimate it. The "e" in eGFR stands for estimated: the lab takes your blood creatinine result and applies an equation that also uses your age and sex.
Creatinine is a waste product of normal muscle turnover; the kidneys clear it, so when filtration falls, creatinine rises. Our article on creatinine covers that side of the story, and the metabolic panel guide explains the electrolytes and other tests usually reported with it.
How Ontario labs calculate it
Community and hospital laboratories in Ontario report eGFR using the CKD-EPI 2021 equation, which uses creatinine, age and sex and no longer includes an adjustment for race. The Ontario Renal Network provides guidance on the race-free equation for primary care, and its KidneyWise toolkit is the reference most Ontario family practices use for kidney testing. Because the calculation is standardized, an eGFR from Bio-Test can be compared with one from another Ontario lab, provided the creatinine methods are aligned, which they are across accredited laboratories.
What the numbers mean
eGFR is reported in millilitres per minute per 1.73 square metres of body surface area. The categories used internationally, and by the Ontario Renal Network, are:
- 90 or above: normal or high filtration
- 60 to 89: mildly decreased; common with age and not by itself a disease
- 45 to 59: mildly to moderately decreased
- 30 to 44: moderately to severely decreased
- 15 to 29: severely decreased
- Below 15: kidney failure
Two cautions. First, eGFR drifts down gradually with normal ageing, so a value in the 60s in a person in their seventies may be entirely expected. Second, many labs report values above 90 simply as ">90" rather than a precise figure, because the equation is less exact at the upper end. What matters most to your physician is the trend over time and whether there is also protein in your urine.
Why one low result is not a diagnosis
Chronic kidney disease is defined as reduced kidney function or kidney damage that persists for more than three months. The Ontario Renal Network's KidneyWise pathway is explicit that a single eGFR below 60 does not by itself mean CKD; the test is repeated after three months, together with a urine albumin-to-creatinine ratio (ACR), before any conclusion is drawn. eGFR can dip temporarily for reasons that have nothing to do with long-term kidney health:
- Dehydration, a hot day, or a stomach bug in the days before the test
- A very high-protein meal or creatine supplements, which raise creatinine
- Some medications, including common anti-inflammatories, taken shortly before
- Unusually high muscle mass, which raises creatinine without any kidney problem, or very low muscle mass, which can make eGFR look better than it is
If your result is lower than expected, your physician will usually look at your previous values, check a urine ACR, and repeat the blood test rather than act on one number. If they want a second opinion on your filtration, they may order cystatin C, a different marker less affected by muscle mass.
Who gets eGFR checked, and how often
Your provider may order creatinine and eGFR as part of a routine panel, but regular monitoring is particularly common if you have diabetes, high blood pressure, heart disease, a family history of kidney disease, or take medications that the kidneys clear or that can affect them. People living with diabetes are typically checked at least yearly along with a urine ACR. Creatinine and urinalysis are insured laboratory services in Ontario when ordered by an authorized practitioner; see what OHIP covers for the general rules.
Preparing for the test
A creatinine and eGFR needs no special preparation on its own. Drink water normally in the day before; do not arrive dehydrated. If your requisition also lists a fasting test, follow the fasting instructions for the whole visit. If a urine ACR is ordered alongside, a first-morning sample is preferred; our guide to urine tests and how to collect them explains the steps and how to bring a sample in. Avoid a heavy workout the day before if you can, since strenuous exercise can nudge creatinine up for a day or so.
Tracking your kidney numbers over time
Because trend matters more than any single value, keep your results together. The Bio-Test app groups kidney results, creatinine, eGFR and urine ACR, by body system and charts them across visits against the lab's own reference range, and it lets you add reports from other laboratories so your physician can see the whole picture. Whatever you notice in the numbers, questions about what they mean for you belong with your physician or nurse practitioner.
Checking your kidneys in Ottawa
Creatinine and eGFR are drawn on a walk-in basis at every one of Bio-Test's 11 patient service centres across Ottawa-Carleton and Eastern Ontario, and you can book a time online if you prefer. Bring your requisition and health card, drink water beforehand, and read our preparation guide if fasting tests share the form. If your provider wants a urine sample as well, ask at the desk for the container when you arrive.