Renin (Direct) Unit Converter
Renin (Direct) Unit Converter
ng/L, pg/mL, ng/dL and ng/100 mL are four labels for two numbers, and converting between them is arithmetic. The two things a renin report actually needs — the mIU/L calibration and the relationship to plasma renin activity — are neither of them conversions, and this page keeps them off the ladder and explains why.
Direct renin converter
Prefix arithmetic onlyDirect renin concentration 15 pg/mL
The ladder, and the two things that are not on it
1 ng/dL = 1 ng/100 mL = 10 ng/L = 10 pg/mL
so ng/dL = pg/mL ÷ 10, and pg/mL = ng/dL × 10
- ng/L = pg/mL
- one nanogram in a litre is one picogram in a millilitre. There is no conversion factor here at all; a laboratory that changes from one label to the other has changed nothing about the result
- ng/dL = ng/100 mL
- a decilitre is 100 mL, so these are the same unit spelt two ways. Both are ten times the ng/L figure, because a decilitre is a tenth of a litre
- no molar unit
- renin is an enzyme measured by immunoassay against a calibrator, not a small molecule with a molar mass you can divide by. pmol/L appears on some conversion sites; it has no defensible basis for an immunoassay result and is not offered here
- mIU/L and µIU/mL
- deliberately absent from the dropdown. These are a CALIBRATION against a WHO international standard, not a conversion, and each manufacturer calibrates separately. The published factors disagree — see the table below — so the only correct one is the one your own laboratory states
- plasma renin activity
- a different measurand entirely, not another unit for this one. PRA measures how much angiotensin I the plasma generates per hour; direct renin concentration measures how much renin protein is there
Worked example
Direct renin concentration 15 pg/mL
15 pg/mL is 15.0 ng/L — the same number, because the two units are identical
15 ÷ 10 = 1.50 ng/dL, which is also 1.50 ng/100 mL
In mIU/L it is somewhere between 25 and 33, depending on which published factor you use — which is the reason that unit is not in the dropdown above
Against plasma renin activity it corresponds to roughly 2 ng/mL/h, with a plausible range of about 1.5 to 2.7 — a correspondence, not a conversion
The mIU/L calibration: two published factors for one step
| Direction | Factor | Source |
|---|---|---|
| pg/mL → µIU/mL (mIU/L) | × 1.67 | UNITSLAB renin page, first of two factors offered |
| µIU/mL (mIU/L) → pg/mL | × 0.6 | UNITSLAB, reciprocal of the above |
| pg/mL → µIU/mL (mIU/L) | × 2.2 | UNITSLAB renin page, second of two factors offered |
| µIU/mL (mIU/L) → pg/mL | × 0.45 | UNITSLAB, reciprocal of the above |
Direct renin concentration against plasma renin activity
| Quantity | What is measured | Unit |
|---|---|---|
| Direct renin concentration (DRC) | The mass of renin protein present, by immunoassay against a calibrator | pg/mL, ng/L or mIU/L |
| Plasma renin activity (PRA) | The rate at which the plasma generates angiotensin I during a timed incubation — an enzymatic rate, which depends on the patient’s angiotensinogen as well as on renin | ng/mL/h |
| Stated correspondence | 1 ng/mL/h of PRA ≈ 7.6 pg/mL of DRC, range 5.5 to 9.7 | Warde Medical Laboratory test update |
Four labels, two numbers, and two things that are not conversions
The unit ladder on this page is the least interesting thing about it. A nanogram per litre and a picogram per millilitre are the same concentration: a litre is a thousand millilitres and a nanogram is a thousand picograms, so the two thousands cancel and the number does not move. A decilitre is a tenth of a litre, so ng/dL is ten times ng/L, and ng/100 mL is simply ng/dL with the decilitre spelt out. Four labels, two numbers, no measured constant anywhere. If that is all you came for, the answer is above.
The two questions that actually cause trouble on a renin report are both absent from that dropdown, and their absence is the point. The first is mIU/L, or equivalently µIU/mL. That is not another metric prefix; it is a calibration against a World Health Organization international standard, and each manufacturer establishes its own relationship to that standard. UNITSLAB, one of the most widely used unit-conversion references in laboratory medicine, publishes two different factors for the same step on the same page — multiply pg/mL by 1.67, or multiply pg/mL by 2.2 — and states plainly that several factors exist depending on the method. Both are correct for some instrument. Neither is correct for all of them. A renin of 15 pg/mL becomes 25 mIU/L or 33 mIU/L depending on which you pick, and since that number goes into the denominator of the aldosterone-renin ratio, the choice can move a screening result across its threshold. Putting either factor into a unit selector would present a calibration as an identity, so this page puts both in a table instead, with the instruction that the only correct factor is the one your own laboratory publishes for its own analyser.
The second is plasma renin activity, and the confusion here is deeper because it is not a unit problem at all. PRA and DRC are different measurands. PRA incubates the patient’s plasma and measures how much angiotensin I appears per millilitre per hour, so it reports an enzymatic rate that depends on the concentration of renin’s substrate — the patient’s own angiotensinogen — as much as on the renin itself. That is why PRA moves with oestrogen, with pregnancy and with anything else that changes angiotensinogen, independently of renin secretion. DRC is an immunoassay that counts renin protein and is blind to the substrate. Warde Medical Laboratory’s test update, issued when they moved from one assay to the other, gives the practical correspondence: 1 ng/mL/h of PRA approximately equals 7.6 pg/mL of DRC, with a range of 5.5 to 9.7 — and states in the same paragraph that there is no precise conversion factor between the two methods and that it varies patient to patient. Use it to read an old report next to a new one. Do not use it to compute anything.
This matters most at the aldosterone-renin ratio, which is why this page has no reference interval of its own. A ratio built on DRC is a different quantity from a ratio built on PRA — different denominator, different units, different numbers — and its cut-off has to be one that was derived against DRC by a laboratory using that assay. Our aldosterone-renin ratio calculator computes against PRA and says so on its own page. Reading a DRC-based ratio against a PRA-derived threshold, or the reverse, is the single commonest way this pair of tests is misread, and no unit converter can rescue it. The reference interval is missing for the same reason: direct renin intervals are nearly always published in µIU/mL, and rendering one in pg/mL would require exactly the calibration factor this page has just argued you cannot rely on. Take the interval from the report that the result came on.
Frequently asked questions
Is ng/L the same as pg/mL for renin?
Yes, exactly and always. A nanogram in a litre is a picogram in a millilitre; the prefixes and the volumes both differ by a thousand and cancel. A laboratory that switches between these two labels has changed nothing about the result, and no multiplication is needed.
How do I convert renin from pg/mL to mIU/L?
You cannot do it reliably from a published table. mIU is a calibration against a WHO international standard that each manufacturer establishes separately, so the factors disagree: UNITSLAB publishes both pg/mL × 1.67 and pg/mL × 2.2 on the same page. Use the factor your own laboratory states for its own analyser, or ask for the result reported in the unit you need.
Can plasma renin activity be converted to direct renin concentration?
Not as arithmetic. They measure different things — PRA is the rate of angiotensin I generation, DRC is the amount of renin protein — and Warde Medical Laboratory, which publishes the most-quoted correspondence, states there is no precise conversion factor. As a bridge for reading an old report, 1 ng/mL/h of PRA is approximately 7.6 pg/mL of DRC, with a range of 5.5 to 9.7.
Why does renin have no molar unit here?
Renin is an enzyme measured by immunoassay against a calibrator, not a small molecule with a fixed molar mass that a mass concentration can be divided by. Some conversion sites offer pmol/L for renin; there is no defensible basis for it in an immunoassay result and it is not offered on this page.
Does the aldosterone-renin ratio work the same way with direct renin?
No. A ratio computed against direct renin concentration is a different quantity from one computed against plasma renin activity, with a different denominator and different units, so it needs a cut-off derived for that denominator by a laboratory using that assay. Check which renin measurement your ratio was calculated from before comparing it with any published threshold.
Why does this page not show a reference interval?
Because direct renin reference intervals are almost always published in µIU/mL, and displaying one in pg/mL would need the manufacturer-specific calibration factor that this page argues you cannot rely on. An interval that contradicts the page it sits on is worse than none, so take the interval from the report the result came on.
Related calculators
References
- Warde Medical Laboratory. Test Update: Renin and Aldosterone/Renin Ratio. “1 ng/mL/hr of plasma renin activity approximately equals 7.6 pg/mL of direct renin concentration (range 5.5 to 9.7)”; “There is no precise conversion factor between the two different methods.”
- UNITSLAB. Renin unit conversion. Publishes both pg/mL × 1.67 and pg/mL × 2.2 to µIU/mL (mIU/L), with the note that several conversion factors exist depending on the method.
- Funder JW, Carey RM, Mantero F, et al. The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016;101(5):1889–1916. doi:10.1210/jc.2015-4061
- Stowasser M, Ahmed AH, Cowley D, et al. Comparison of Seated With Recumbent Saline Suppression Testing for the Diagnosis of Primary Aldosteronism. J Clin Endocrinol Metab. 2018;103(11):4113–4124. doi:10.1210/jc.2018-01394
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.