eGFR
Also called: estimated glomerular filtration rate, kidney function test
What it means
eGFR stands for estimated glomerular filtration rate, a blood test result that shows how well your kidneys are filtering waste. Doctors use it to check kidney function and, in bone health, to spot kidney disease that can weaken bones.
Kidney function directly affects calcium, vitamin D activation, and parathyroid hormone balance, all of which shape how strong or fragile your bones become.
eGFR is calculated from a blood creatinine level along with your age, sex, and sometimes race, giving an estimate of how much blood your kidneys filter each minute. It's one of the most common tests used to screen for and track chronic kidney disease, and it's often included on routine blood panels.
Kidneys and bones are closely linked. When eGFR drops, the kidneys struggle to activate vitamin D and clear phosphorus properly. This can trigger a chain reaction: phosphorus builds up, a hormone called FGF23 rises, active vitamin D (calcitriol) falls, calcium drops, and the parathyroid glands respond by releasing more parathyroid hormone. Over time this can lead to a bone and mineral disorder tied to chronic kidney disease, sometimes needing specialized testing like a bone biopsy to sort out exactly what's happening in the bone.
Because of this connection, eGFR is a standard part of a basic bone health workup alongside tests like calcium, phosphate, vitamin D, and parathyroid hormone. If your eGFR is low, your doctor may want to look more closely at your bone health and may adjust which osteoporosis treatments are appropriate, since some medications are handled differently by the kidneys. Any decisions about testing or treatment should be made with your doctor.
Kidney function, measured by eGFR, shapes calcium, vitamin D, and hormone balance that your bones depend on.
Where this leads
WordeGFR hints at how your body handles vitamin D activation. Curious what happens to bones when vitamin D itself runs low?
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Related words
Chronic kidney disease is a long-term decline in kidney function that can disrupt vitamin D activation and the…
CKD-MBD is a bone and mineral problem caused by chronic kidney disease. As kidneys fail, they can't properly balance…
A parathyroid hormone (PTH) test measures the amount of PTH in your blood, usually alongside calcium, to help find…
FGF23 is a hormone made by bone cells that tells the kidneys how much phosphate to keep or remove and helps regulate…
Secondary hyperparathyroidism is when the parathyroid glands make too much PTH because of a problem elsewhere, like…
Vitamin D deficiency means your body doesn't have enough vitamin D, which is needed to absorb calcium and keep bones…
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
