[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Renal, fluids and acid–base](https://durgical.com/en/physiology/#s-renal) › Renal clearance

[Physiology](https://durgical.com/en/physiology/) · [Renal, fluids and acid–base](https://durgical.com/en/physiology/#s-renal)

# Renal clearance

- Measurement
- Exam priority: high

Clearance tells how much plasma the kidney cleans of a substance per minute. It measures filtration and shows whether the tubule reabsorbs or secretes.

Updated 2026-11-01

Also called: Clearance

**See it in 3D:** [Kidneys](https://durgical.com/en/anatomy/kidney/)

## Key points

- C = (U × V) / P: urine concentration times urine flow, divided by plasma concentration.
- Inulin is filtered and nothing else, so its clearance equals GFR (≈ 125 mL/min).
- Creatinine is filtered and slightly secreted, so it overestimates GFR a little; it is the everyday marker.
- Clearance > GFR = net secretion (PAH, penicillin); clearance

### The nephron: segments, transporters and diuretics

**GFR** ≈ 125 mL/min **Filtrate** ≈ 180 L/day **Urine** ≈ 1–2 L/day

Tap a nephron segment: what it reabsorbs, its transporters, the hormones, the diuretics that act there and the classic disorders.

- Glomerulus and arterioles
- Proximal tubule
- Thin descending limb
- Thin ascending limb
- Thick ascending limb
- Distal convoluted tubule
- Collecting tubule and duct
- Juxtaglomerular apparatus (macula densa)
- Cortex
- Medulla
- Interstitial osmolality (≈ 300 → 1200 mOsm/kg)

Illustrative schematic drawn by Durgical (a long-loop juxtamedullary nephron); proportions and percentages are approximate and not for clinical decisions.

## Equations

**Clearance**Cx = (Ux × V) / Px

**U x**
urine concentration

**V**
urine flow (mL/min)

**P x**
plasma concentration

Units of flow (mL/min). Use the same concentration unit above and below.

**Fractional excretion**FEx = Cx / GFR = (Ux × PCr) / (Px × UCr)

**P Cr, U Cr**
plasma and urine creatinine

FENa **Tubular balance**Excretion = Filtration − Reabsorption + Secretion

**Filtration**
GFR × P_x (filtered load)

Comparing excretion with the filtered load shows whether reabsorption or secretion dominates.

## Typical clearances

| Parameter | Value | Note |
| --- | --- | --- |
| Inulin | ≈ 125 mL/min | = GFR |
| Creatinine | ≈ 110–140 mL/min | slightly above GFR |
| PAH | ≈ 585–625 mL/min | ≈ effective renal plasma flow |
| Urea | ≈ 50–70 mL/min | ≈ 40–50% reabsorbed |
| Glucose | ≈ 0 mL/min | fully reabsorbed below threshold |

Approximate values for a healthy adult at rest; each laboratory sets its own ranges.

## Reading clearance against GFR

| Result | What the tubule does | Example |
| --- | --- | --- |
| C = GFR | Neither reabsorbs nor secretes | Inulin |
| C GFR | Net secretion | PAH, penicillin, creatinine (a little) |
| C ≈ 0 | Reabsorbs all that is filtered | Glucose, amino acids |

## Clinical notes

- Estimated GFR (eGFR) from serum creatinine stages chronic kidney disease; muscle mass (elderly, malnourished, amputees) biases it.
- Some drugs (trimethoprim, cimetidine) block creatinine secretion: creatinine rises without a fall in true GFR.
- In acute kidney injury, FENa helps separate a prerenal cause (2%).

## Memory aid

'U times V over P': what leaves per minute divided by what is in plasma. Beat inulin and the tubule must have secreted.

## Test yourself

Think of the answer, then tap the question to see it.

## A substance has a clearance of 300 mL/min with a GFR of 120 mL/min: what does the tubule do with it?

It secretes it: more is excreted than filtered, so there is net tubular secretion (like PAH or penicillin).

## Why does creatinine clearance slightly overestimate GFR?

Besides being filtered, some creatinine is secreted in the proximal tubule, and that extra amount in urine raises the calculated clearance.

## Why can PAH clearance estimate renal plasma flow?

PAH is filtered and the rest is almost completely secreted in a single pass, so nearly all plasma reaching the kidney is cleared of PAH.

## Why does glucose appear in urine in uncontrolled diabetes when glucose clearance is normally zero?

When blood glucose rises, the filtered load exceeds the transport maximum of proximal tubule SGLTs; the excess is not reabsorbed and is excreted.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/renal-clearance/)

## See it in 3D

The structures of Durgical's 3D anatomy where it happens.

- [Kidneys](https://durgical.com/en/anatomy/kidney/)

## Related topics

- [Measuring GFR and plasma flow: inulin, creatinine, PAH and filtration fraction](https://durgical.com/en/physiology/measuring-gfr-and-plasma-flow-inulin-creatinine-pah-and-filtration-fraction/)
- [Glomerular filtration: the barrier and its determinants](https://durgical.com/en/physiology/glomerular-filtration-the-barrier-and-its-determinants/)
- [Glucose transport maximum and renal threshold](https://durgical.com/en/physiology/glucose-transport-maximum-and-renal-threshold/)
- [Urine dilution, free water and osmotic diuresis](https://durgical.com/en/physiology/urine-dilution-free-water-and-osmotic-diuresis/)
- [Tubular secretion of organic acids and bases](https://durgical.com/en/physiology/tubular-secretion-of-organic-acids-and-bases/)

## Related conditions

- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/)

## In Biochemistry

- [Creatinine and estimated glomerular filtration rate (eGFR)](https://durgical.com/en/biochemistry/topics/creatinine-and-estimated-glomerular-filtration-rate/)
- [Urea and blood urea nitrogen (BUN) as lab tests](https://durgical.com/en/biochemistry/topics/urea-and-blood-urea-nitrogen-as-lab-tests/)
- [Glucose](https://durgical.com/en/biochemistry/molecules/glucose/)

## In Pharmacology

- [Benzylpenicillin (penicillin G)](https://durgical.com/en/pharmacology/benzylpenicillin/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [25.5 Physiology of Urine Formation](https://openstax.org/books/anatomy-and-physiology-2e/pages/25-5-physiology-of-urine-formation) (OpenStax (Rice University), 2022); [25.6 Tubular Reabsorption](https://openstax.org/books/anatomy-and-physiology-2e/pages/25-6-tubular-reabsorption) (OpenStax (Rice University), 2022); [Chronic Kidney Disease](https://www.ncbi.nlm.nih.gov/books/NBK535404/) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 28). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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Representative model, for educational purposes only.

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