Confused by American Standard Unit for Free Test

The number they typically mention in a good Free T level is 30 and above.
My Free Test is 529 pmol/L.

Is it ng/dL or ng/mL or other variations of ng or pg/mLthat I see and typically referenced? LOL

Component Your Value Standard Range Flag
Testosterone Free Calculated 529 pmol/L 163 - 473 pmol/L H
SHBG 24 nmol/L 21 - 77 nmol/L
Testosterone Total 20.7 nmol/L 6.7 - 25.7 nmol/L

144 pg/mL


529 pmol/L * 1 nmol / 1000 pmol * 288.431 ng / nmol * 1 L / 10 dL = 15.3 ng/dL = 153 pg/mL to 3 sig figs as per measurement

Note: 1 ng/dL = 10 pg/mL

What you typically see is ng/dl if you are getting an accurate equilibrium dialysis free T test. Ref ranges vary from 5 up to 28 ng/dl depending on lab. Your number above is 15.3 ng/dl for comparison.

Also there’s a misleading direct RIA fT test that is typically reported in pg/ml.

You’d have to post an old test or do some more hw to determine what you typically get back from lab.

Who is they?

Your TT above is 597 ng/dl. You can use online calculator to plug in SHBG and TT and confirm fT number i converted for you.

Another slightly rounded set of conversion factors here:

Reinforces a point about roundoff error on intermediate calculations i made in another post.


This one, for the 30 FT figure you mentioned. I like 25-35ng/dL. But also use the calculated method since direct measure is so problematic

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My internet conversion gave 153pg/mL

I love the respect for significant digits


Internet conversion:

Internet conversions i saw gave 152 due to roundoff error. Which one did you use?

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Actually mine gave me 152.5. It ignored the 3significant digits of the measured value.

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Various Forums and YouTube TRT guys state many people don’t feel “optimized” until their Free T hits 25 and better yet, 30+.

Holy crap, so despite 15.3 being HIGH according to Canadian labs, I’m at half of what these guys are saying, Was it another unit they are talking about? LOL

Thank you tareload and all! :+1:t2:

You are correct. 30 to 50 ng/dl fT is touted. My pleasure.

Like I’ve said this advice will and has hurt people.

He’s talking about YOU at 1:25 @phil65 LMFAO.


Holy CRAP! He said “15.8”. Just 0.5 off!!! :scream::crazy_face::joy:

Wow… so literally at HALF of where Free T often “optimizes” people, despite being HIGH.

I’d have to see the particular assay you used to measure TT. The upper ref range 25.7 nmol/l (741 ng/dl) tells me it doesn’t have 1:1 correspondence with say Labcorp LC/MS-MS assay which has a higher ref range. So I’d put 28 ng/dl as true top of fT ref range. It’s all very arcane.

But to your point, I have a hard time understanding a guy on TRT running a fT of 50 ng/dl long term. But that’s just me.

This optimization lingo is all bullshit. What are we optimizing? What’s the time horizon? Blah blah. See my TRT thread if you want more info and entertainment.

Best wishes.

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I feel good at 25+ng, but have also felt just fine at 15ng. I would say that’s as low as I’d want to go, personally

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The issue as framed above is that the fT above is calculated on SHBG and TT. Since the TT above wasnt LCMS we dont know the absolute accuracy of the calculated fT above. Relative vs absolute error.

So is his 15 ng/dl really 15 or 20?

Anyway i have probably beaten this enough.


Yeah that is a good point

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I think a lot of times people are freaking on the upper ref range of their TT assay and think there is a major conspiracy. Sure TT levels are dropping some [obesity, etc] but the other reason is labs are using an immunoassay for TT thats highly correlated with LCMS result but the parity plot is not slope of 1 and intercept of 0. So they see the upper ref range at 600 or 700 ng/dl and are like WTF?

Then you take this result and calculate fT which propagates the absolute error on the TT result.


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As an aside and anecdotally, calculated Free T has been very inaccurate for me. I always advise against it.

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Tru-T or Vermeulen? Both?

Love to look at your head to head data vs LC/MS-MS+ED/UF.

Is that back in your log?

Haha i went and looked. Yep it was quite a gap with cfTV. :grinning:

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Haha I was checking myself it’s been a long time since I updated it. I remember I used this website for Tru-T:

For example one of my blood tests from 6 months ago or so I was at 1300ng/dL TT, 40nmol/L SHBG, and my Free T was at 28ng/dL (equilibrium dialysis).

Tru-T tells me calculated Free T with those values should be 46.5ng/dL. That’s completely off

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I put more confidence in Vermeulen even though TruT is supposed to be the ultimate. I dont see that from the literature and data.

I have a bet that Tru-T will be shown flawed once the CDC fT harmonization work is complete.


cfTV yields 30.5 ng/dl. Similar to the at most 20-30% overprediction max i have seen vs lc/ms-ms + ED.

Thanks for new point.