What does an eGFR of 45 mean?
An eGFR of 45 mL/min/1.73m² sits at the lower edge of KDIGO band G3a, which the guideline describes as "mildly to moderately decreased" filtering. It is a result doctors follow up on, and it should not be left unread — but it is not an emergency and it is not kidney failure. A single reading also cannot stage chronic kidney disease: that needs the level to stay there for more than three months, together with a urine test for albumin.
45 mL/min/1.73m² is the conventional unit used by KDIGO and by labs in most countries. The same result in SI units is 0.75 mL/s/1.73m², because 1 mL/min/1.73m² equals roughly 0.0167 mL/s/1.73m². If you see a figure such as 0.75 on a report from another country, it is the same measurement in different clothes.
What this test measures
eGFR stands for estimated glomerular filtration rate — an estimate of how much blood the tiny filters in your kidneys clean each minute. The "1.73m²" means the number is adjusted to a standard adult body size so results can be compared between people. It is an estimate, not a direct measurement. The lab measures creatinine, a waste product your muscles release into the blood, and an equation converts it using your age and sex. In practical terms, 45 is roughly under half the filtering rate typical of a healthy young adult — but "typical" is doing a lot of work in that sentence, because the estimate can be thrown off by unusually high or low muscle mass, a recent illness or infection, dehydration, a large meat meal before the test, pregnancy, and some medicines. Different labs use different versions of the equation too, so numbers from different places are not always directly comparable.
Where 45 mL/min/1.73m² sits
The KDIGO chronic kidney disease guideline sorts eGFR into "G stages", all in mL/min/1.73m²: G1 is 90 or above, G2 is 60–89, G3a is 45–59 (mildly to moderately decreased), G3b is 30–44, G4 is 15–29, and G5 is under 15. A result of 45 sits at the very bottom of G3a, next to the G3b band. Two things are worth holding on to. First, KDIGO does not let a single blood test stage kidney disease — the result has to persist beyond three months. Second, eGFR is only one axis of the staging chart; the other is a urine test measuring albumin (albumin-to-creatinine ratio, or ACR), and two people with the same eGFR but very different albumin results are in quite different positions. Only a doctor who can see both, plus your history, past results and what else is going on, can interpret this properly.
What to do next
- Contact the doctor or clinic that ordered the test rather than waiting for your next routine appointment. A result in this band is meant to be reviewed by someone who can see your whole record.
- Ask whether a urine albumin test (ACR) has been done, and what it showed. It is the second half of the KDIGO picture and it strongly shapes how this eGFR is read.
- Gather any older kidney results. Whether 45 is a new number or a stable one for years changes the conversation completely.
- Bring a full list of everything you take — prescribed, bought without a prescription, herbal, traditional or supplement — so your doctor can review it. Do not stop or change anything on your own.
- Ask directly what the plan is: when the next test will be, whether a referral is being considered, and what would count as a reason to come back sooner.
Common questions
Is an eGFR of 45 serious?
It is a result doctors take seriously enough to follow up, and it should not be ignored. It is also not an emergency by itself and it is not kidney failure. What it means for you depends on your urine albumin result, your other conditions, and what the number has been doing over time — which is why it needs your doctor rather than a chart.
Does an eGFR of 45 mean I will need dialysis?
No. Most people whose results sit in this band never reach that point. What happens next is shaped by many things at once — the underlying cause, the urine albumin result, blood pressure, and the trend over years — and nobody can predict one person's future from one number. It is a reasonable question to ask your doctor directly.
Can stage G3a be reversed?
Sometimes filtering improves, particularly when something temporary pushed the number down. Often it stays roughly where it is for a long time. Because outcomes vary so much between individuals, no honest source can promise either way, and anyone online who guarantees an outcome is guessing.
What makes eGFR drop to 45?
Long-term conditions that affect blood vessels and the kidneys are the most common background causes worldwide. Short-term things can also lower a single reading: dehydration, an infection, a recent illness, or something you have recently taken. Working out which applies to you is a job for the doctor who holds your full record.
Should I see a kidney specialist?
Many people at this level are looked after by their usual doctor, with referral considered if the number is falling, if there is a lot of albumin in the urine, or if the cause is unclear. Ask your doctor whether referral makes sense in your case — it is a fair and useful question.
I have no symptoms at all. Is that strange?
No, it is the usual pattern. Reduced filtering is often completely silent at this level, which is why it tends to be found on a blood test rather than because someone feels ill. Feeling well is not a reason to skip the follow-up.
Could this reading be a mistake?
Single results can mislead, and labs vary in equipment and in which version of the eGFR equation they use. That is exactly why guidelines ask for a repeat before drawing conclusions, and why your doctor may also arrange a different kind of blood test to check the estimate.