Testosterone Dosage Calculator
“How many mL is 100 mg of testosterone?” is the most asked question in TRT forums, and it has no answer until you read the vial. A milliliter is a volume; a milligram is a dose; the vial’s concentration connects them. A 200 mg/mL vial turns 100 mg into 0.5 mL, while a 250 mg/mL vial turns the same 100 mg into 0.4 mL. This calculator does that division for you, splits the weekly dose across your injection schedule, converts the volume to insulin-syringe units, and tells you how long a 10 mL vial lasts. If you are tracking the body-composition side of therapy, our BMI and waist circumference calculator and workout calorie calculator cover training and measurement.
Quick Answer
The one formula that matters
Insulin syringe units = mL x 100
Everything else is bookkeeping. The formula has exactly one trap: the concentration. Testosterone cypionate in the US is most commonly 200 mg/mL, but 100 mg/mL vials exist; enanthate is 200 mg/mL in the US and frequently 250 mg/mL internationally; compounded products can be anything. The vial label is the only authority. Every “I accidentally took the wrong dose” story in TRT forums traces back to someone assuming 200 mg/mL.
Insulin syringes read in units where 100 units = 1 mL, which is why 0.25 mL becomes 25 units. For the small volumes of twice-weekly or daily protocols, 29 to 31 gauge insulin syringes give far better precision than 3 mL syringes, and many patients find them more comfortable as well.
Common vial concentrations
| Ester | Common concentration | 100 mg = | Notes |
|---|---|---|---|
| Cypionate (US) | 200 mg/mL | 0.5 mL | Also available as 100 mg/mL; cottonseed oil base |
| Enanthate (US) | 200 mg/mL | 0.5 mL | Sesame oil base |
| Enanthate (intl) | 250 mg/mL | 0.4 mL | Check the label, not the country stereotype |
| Propionate | 100 mg/mL | 1.0 mL | Shorter half-life; injected every other day |
| Xyosted (auto-injector) | 50/75/100 mg per 0.5 mL | Fixed | Pre-measured; the one product approved for subcutaneous use |
Worked example: 100 mg weekly, split twice
Twice-weekly splitting is popular because cypionate and enanthate peak a day or two after injection and then decline; smaller, more frequent doses flatten the curve, which many patients feel as steadier energy and mood. Daily microdosing takes this further: 100 mg per week becomes about 14.3 mg (0.071 mL, 7.1 units) daily on a 200 mg/mL vial. The total weekly milligrams never change; only the per-injection volume does, which is exactly what the calculator recomputes when you change the frequency.
What competing calculators get wrong
TRT dose calculators mostly do the core division correctly, then fumble the context. The common failures: hardcoded 200 mg/mL with no way to enter anything else, which silently overdoses anyone with a 250 mg/mL vial by 25%; no injection-frequency splitting, forcing users to redo the math for twice-weekly protocols; no insulin-unit readout, even though most patients on split protocols use insulin syringes; and zero mention of the monitoring that makes TRT safe, presenting dose math as if the number were the whole therapy. One popular tool also conflates “1 mL per week” with a dose, when 1 mL can mean 100 mg or 250 mg depending on the vial.
Our winning moves: selectable ester concentrations plus a custom field, per-injection and weekly volumes, the insulin-unit conversion, vial-duration planning, and the concentration warning printed with every result. The article pairs the math with the medicine: hematocrit and PSA monitoring per Endocrine Society guidance, the fertility consequence (exogenous testosterone suppresses sperm production), and the fact that dose adjustments follow labs and symptoms, never a calculator.
Monitoring that makes TRT safe
The Endocrine Society guideline frames testosterone therapy as a monitored treatment, not a supplement routine. Baseline and follow-up labs include total testosterone (targeting the mid-normal range, roughly 450 to 600 ng/dL), hematocrit (therapy is withheld or reduced if it exceeds 54% because of erythrocytosis risk), and PSA with prostate evaluation in men over 40. Therapy is not started with hematocrit above 54%, untreated severe sleep apnea, or active prostate or breast cancer, and it is not for men planning fertility in the near term. If costs are part of your planning, our health insurance cost calculator can help you compare coverage for labs and visits.
- Milliliters = milligrams / concentration. Read the concentration off your vial every time.
- 100 mg from a 200 mg/mL vial is 0.5 mL; from a 250 mg/mL vial it is 0.4 mL.
- Splitting the weekly dose into 2+ injections steadies levels; the weekly milligrams stay the same.
- On insulin syringes, 100 units = 1 mL. Small volumes need small syringes for accuracy.
- TRT requires lab monitoring (testosterone, hematocrit, PSA) and suppresses fertility.
- Dose changes follow labs and symptoms under clinician direction, never a web calculator.
Frequently Asked Questions
0.5 mL from a standard 200 mg/mL vial (100 / 200 = 0.5). From a 100 mg/mL vial it would be 1.0 mL. The answer is meaningless without the concentration, so always check your vial label.
Very little in practice: both are long-acting esters with similar half-lives, dosed 50-100 mg weekly or 100-200 mg every two weeks. They differ in carrier oil (cottonseed vs sesame) and in common concentrations by country. Propionate is the short-acting one, needing every-other-day injections.
Many clinicians and patients prefer it because smaller, more frequent doses produce steadier testosterone levels with lower peaks and shallower troughs. The weekly total in milligrams does not change. Your prescriber sets the schedule based on your labs and symptoms.
Insulin syringes are marked in units: 100 units = 1 mL. So 0.25 mL = 25 units, 0.2 mL = 20 units, and 0.5 mL = 50 units. Use a 0.3 or 0.5 mL syringe for small TRT volumes so the markings are readable.
No. Dose adjustments follow lab values (testosterone, hematocrit, estradiol, PSA) and clinical evaluation, not symptoms alone. Raising the dose without monitoring increases erythrocytosis, blood pressure, and estrogen-conversion risks without proven added benefit.
Yes. Exogenous testosterone suppresses the pituitary signals that drive sperm production and can cause prolonged azoospermia. The Endocrine Society recommends against testosterone therapy in men planning fertility in the near term; fertility-preserving alternatives exist and require specialist discussion.
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References
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. Monitoring standards: hematocrit, PSA, testosterone targets.
- The Blood Project. Testosterone Therapy and Erythrocytosis. Endocrine Society thresholds: hold therapy above 54% hematocrit; relative contraindication above 50%. Accessed October 19, 2026.
- National Institutes of Health. Testosterone Formulations: Supply and Dosing Table. PMC. Cypionate 100/200 mg/mL, enanthate 200 mg/mL, gels, pellets, and dosing ranges. Accessed October 19, 2026.
- National Institutes of Health. Expert Opinion on the Diagnosis and Management of Male Hypogonadism. PMC. Diagnostic cutoffs (300 ng/dL), contraindications, and monitoring schedules. Accessed October 19, 2026.
- Endocrine Society. Testosterone Therapy in Men With Hypogonadism: Clinical Practice Guideline (full text). Dosing regimens by formulation and safety monitoring. Accessed October 19, 2026.
- Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy. N Engl J Med. 2023;389:107-117. TRAVERSE trial: cardiovascular safety findings in hypogonadal men.
- Snyder PJ, et al. Effects of testosterone treatment in older men. N Engl J Med. 2016;374:611-624. Testosterone Trials: efficacy and safety signals.
- Buckinghamshire NHS Formulary. Testosterone for Hypogonadism in Males: Shared-Care Guideline. Hematocrit and PSA monitoring schedules in practice. Accessed October 19, 2026.