Hematocrit-vs-Dose Individualization
Why High-SHBG and Low-SHBG Men Need Different Protocols
Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.
The written rationale for this grade is still being prepared.
- FDA
- Individualization is a clinical practice, not an FDA-specified protocol
Reference only. Not medical advice.
What can go wrong
Treating to a fixed total-testosterone number while ignoring SHBG and free testosterone can over- or under-dose a patient: a low-SHBG man pushed to a high total can develop early erythrocytosis and side effects, while a high-SHBG man at a 'normal' total may remain symptomatic from low free testosterone. Mass-market protocols that apply one dose and frequency to everyone predictably misfire in the tails of the SHBG distribution.
This is something to take to a clinician. The Atlas can tell you what is known about hematocrit-vs-dose individualization in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
Two men on the identical testosterone dose can have very different free-testosterone levels, symptom responses, and hematocrit trajectories, largely because of sex-hormone-binding globulin (SHBG). A low-SHBG man (often more insulin-resistant, heavier) carries more free testosterone per unit of total, may feel effects and develop erythrocytosis at lower total doses, and frequently does better on smaller, more frequent dosing; a high-SHBG man (often leaner, sometimes older) may show a high total testosterone yet have lower free testosterone and need a different target. Good practice individualizes dose, frequency, and route to the patient's SHBG, hematocrit response, and symptoms rather than to a fixed milligram number.
The same milligram dose lands very differently on a high-SHBG man than a low-SHBG one, which is why one-size protocols misfire.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
How it is supposed to work
Most circulating testosterone is bound to SHBG and albumin; only the free (and loosely albumin-bound) fraction is bioavailable. SHBG therefore determines how much of a given total testosterone is biologically active. Low-SHBG men convert a given dose into more free testosterone, intensifying both wanted effects and dose-related toxicities such as erythrocytosis; high-SHBG men may need attention to free testosterone rather than total. Erythropoietic drive tracks androgen exposure and peak, so SHBG, dose, frequency, and route together shape each man's hematocrit trajectory.
- Free fraction driver
- SHBG concentration
- Low-SHBG phenotype
- More free-T per dose; faster hematocrit rise
- High-SHBG phenotype
- Less free-T per dose; may need frequency/target adjustment
- Tuning levers
- Dose, frequency, route
Safety in detail
This intervention involves significant physiological effects and requires evaluation and monitoring by a qualified physician. Self-administration without medical oversight carries documented health risks.
What it does to fertility
SHBG-based individualization does not change TRT's suppression of spermatogenesis; fertility preservation still requires gonadotropin adjuncts or a fertility-sparing alternative.
What has to be monitored
The bloodwork this needs, and the reason it belongs with a clinician rather than a website.
- SHBG and free testosterone when total is discordant with symptoms
- Total testosterone (timed to protocol)
- Hematocrit/hemoglobin response
- Symptom review
What people get wrong
Often saidThe right TRT dose is the same for everyone
ActuallySHBG, body composition, and individual erythropoietic response make the same dose behave very differently; dosing must be individualized.
Often saidA normal total testosterone means the dose is correct
ActuallyWith abnormal SHBG, total testosterone can mislead; free testosterone and symptoms guide whether the dose fits.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
What we do not know
- Best free-testosterone target and assay for individualized dosing
- Whether SHBG phenotype reliably predicts erythrocytosis risk prospectively
- How much frequency/route adjustment offsets SHBG-driven differences
At a glance
- Key modifier
- SHBG (binds testosterone; sets free fraction)
- Low SHBG
- Higher free-T per total; often heavier/insulin-resistant; erythrocytosis at lower dose
- High SHBG
- Lower free-T per total; may need different target/frequency
- Other modifiers
- Body composition, age, sleep apnea, baseline hematocrit, route
- Practical lever
- Dose, frequency, and route tailored to response, not fixed mg
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Hematocrit-vs-Dose Individualization. A short entry is not a safe entry.
- Timeline. We have not built the dated record of research and regulatory events.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
- Where we land. We have not taken a position on this yet.
Sources
The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.
The studies that matter
Endocrine Society Clinical Practice Guideline (Bhasin et al., JCEM)2018
Recommends considering free testosterone when SHBG is abnormal and individualizing therapy
Literature on SHBG and free-testosterone interpretationvarious
Documents how SHBG shifts the total-to-free relationship and complicates fixed-target dosing