TRT Dosage Calculator
Calculate your personalised testosterone replacement therapy dosage and injection volume based on your prescription and testosterone formulation. This calculator helps you determine the correct amount to inject whilst considering various factors such as concentration, frequency, and administration route.
Your Results
These calculations are estimates for educational purposes. Always consult with your GP or endocrinologist before starting or adjusting TRT. Regular blood tests and medical monitoring are essential for safe testosterone replacement therapy.
How to Use This Calculator
Dosage Calculator
The dosage calculator helps determine your recommended weekly testosterone dose based on your current and target testosterone levels. Enter your current testosterone reading (from a recent blood test), your target level, body weight, age, and SHBG status. The calculator considers these factors to suggest an appropriate starting dose.
Volume Calculator
Once you’ve received a prescription, use the volume calculator to work out exactly how much liquid to draw into your syringe. Simply enter your prescribed dose in milligrams and the concentration of your testosterone preparation. The result shows the volume in millilitres (mL) that you need to inject.
Optimal Dosage Finder
This helps you find the most suitable TRT protocol based on your symptoms, experience level, preferred administration method, and lifestyle. It provides personalised recommendations for testosterone type, dosing frequency, and expected outcomes.
Many people confuse volume (mL) with dose (mg). For example, 1mL of testosterone could contain 100mg, 200mg, or 250mg depending on the concentration. Always check your vial’s concentration and calculate the correct volume to inject.
Testosterone Preparations Available in the UK
| Preparation | Half-Life | Typical Frequency | Recommended Dosing |
|---|---|---|---|
| Testosterone Cypionate | 8 days | Every 3-7 days | 75-100mg every 3-4 days |
| Testosterone Enanthate | 7 days | Every 3-7 days | 80-100mg every 4-6 days |
| Sustanon 250 | Mixed esters | Every 5-7 days | 125mg every 5-7 days |
| Testosterone Propionate | 2 days | Daily or EOD | 20-25mg daily |
| Testosterone Undecanoate | 21 days | Every 10-14 weeks | 1000mg every 10-12 weeks |
| Testosterone Cream | N/A | Once or twice daily | 100-200mg per application |
Microdosing vs Traditional Dosing
Modern TRT protocols favour smaller, more frequent doses over large biweekly injections. Microdosing involves administering testosterone every few days or daily, which maintains more stable blood levels and reduces side effects such as mood swings, oestrogen spikes, and fluctuating energy.
Traditional Dosing
Protocol: 200-250mg every 2-3 weeks
Levels: Large peaks and troughs
Effects: Mood swings, energy fluctuations, increased side effects
Microdosing
Protocol: 75-100mg every 3-4 days
Levels: Stable throughout the week
Effects: Consistent mood and energy, fewer side effects
Daily Dosing
Protocol: 10-20mg daily
Levels: Mimics natural production
Effects: Most stable levels, minimal peaks and troughs
What Your SHBG Level Means
Sex Hormone Binding Globulin (SHBG) is a protein that binds to testosterone in your blood. Your SHBG level significantly affects how you respond to TRT and what dosing frequency works best for you.
Low SHBG (< 20 nmol/L)
Testosterone clears from your system quickly. You may need smaller, more frequent doses (daily or every other day) to maintain stable levels. Consider testosterone propionate or daily cream application.
Normal SHBG (20-50 nmol/L)
Most protocols work well. You can typically use cypionate or enanthate every 3-7 days, or sustanon every 5-7 days. This range offers the most flexibility in dosing frequency.
High SHBG (> 50 nmol/L)
Testosterone stays bound longer, reducing free testosterone. You may need higher doses or more frequent administration. Some patients benefit from daily propionate or cream to increase free testosterone levels.
Injection Sites and Absorption
Where you inject testosterone affects how quickly it’s absorbed and how stable your levels remain. Each injection site has distinct characteristics that can influence your TRT experience.
| Injection Site | Absorption Rate | Advantages | Considerations |
|---|---|---|---|
| Gluteal (buttocks) | Slow and steady | Large muscle, steady release, less frequent injections | Difficult to self-inject, may need assistance |
| Vastus lateralis (thigh) | Moderate | Easy to access, good for self-injection | Can be painful, may cause temporary soreness |
| Deltoid (shoulder) | Faster | Convenient, easy self-injection, smaller volumes | Limited injection volume, not suitable for large doses |
| Subcutaneous (abdomen) | Slower | Smaller needles, less painful, stable absorption | May cause lumps, not suitable for large volumes |
Rotate injection sites to prevent scar tissue buildup and maintain consistent absorption. Create a rotation schedule and keep a log of where and when you inject to avoid using the same site too frequently.
Common Dosing Scenarios
Scenario 1: Starting TRT
You’re prescribed 100mg of testosterone cypionate per week. Your vial is 200mg/mL in a 10mL bottle. How much do you inject?
You’ll inject 0.5mL once weekly, or split it into 0.25mL twice weekly for more stable levels.
Scenario 2: Microdosing Protocol
Your doctor recommends 75mg every 3.5 days (Monday morning and Thursday evening). Same vial: 200mg/mL.
You’ll inject 0.375mL (between the 0.3 and 0.4 marks on your syringe) twice per week, totalling 150mg weekly.
Scenario 3: Sustanon Protocol
You’re prescribed 125mg of Sustanon every 5 days. Your ampoules are 250mg/mL in 1mL ampoules.
You’ll use half an ampoule every 5 days. However, once opened, ampoules must be used immediately, so discuss multi-dose vials with your doctor for more economical dosing.
Frequently Asked Questions
Milligrams (mg) measure the amount of testosterone in your dose, whilst millilitres (mL) measure the liquid volume. The concentration tells you how many mg are in each mL. For example, if your vial is 200mg/mL, then 1mL contains 200mg of testosterone. Always focus on the mg dose your doctor prescribed, then calculate the mL volume needed based on your vial’s concentration.
This depends on the testosterone ester and your individual response. Short esters like propionate require daily or every-other-day injections. Medium esters like cypionate or enanthate work well every 3-7 days. Sustanon can be injected every 5-7 days. More frequent injections generally provide more stable levels and fewer side effects. Your SHBG level also influences optimal frequency—low SHBG typically requires more frequent dosing.
If you miss an injection, take it as soon as you remember, then return to your regular schedule. Don’t double up doses to compensate. If you frequently forget injections, consider setting phone reminders or switching to a less frequent protocol. Missing occasional injections won’t cause serious harm, but consistent missed doses can lead to symptom return and hormone level fluctuations.
Yes, TRT is available on the NHS if you have diagnosed hypogonadism (low testosterone) with symptoms. You’ll need blood tests showing testosterone levels below 12 nmol/L (some areas use 8 nmol/L as the threshold). However, NHS protocols often use older dosing schedules. Private clinics typically offer more modern approaches with microdosing and closer monitoring.
Most men feel best with testosterone levels between 20-30 nmol/L, though the optimal range varies individually. The NHS considers 12-30 nmol/L as normal, but many men with levels below 15 nmol/L still experience symptoms. Your doctor will help determine your target level based on symptom relief whilst monitoring for side effects. The goal is the lowest effective dose that alleviates symptoms.
Both methods are effective. Intramuscular (IM) injection uses longer needles (25mm) into muscle tissue, providing reliable absorption but can be more painful. Subcutaneous (SubQ) injection uses shorter needles (8-13mm) into the fat layer, is generally less painful, and many patients find it easier for self-administration. Some people develop lumps with SubQ injections. Try both methods to see which you prefer, as absorption and results are comparable.
Effects vary by symptom. Some men notice improved energy and mood within 2-3 weeks. Libido improvements typically occur within 3-6 weeks. Changes in body composition (muscle gain, fat loss) take 3-6 months. Maximum benefits for bone density require 12-24 months. Remember that TRT is a long-term treatment, and patience is necessary. If you notice no improvement after 8-12 weeks, discuss dose adjustments with your doctor.
Common side effects include increased red blood cell count, acne, oily skin, testicular shrinkage, and reduced fertility. Some men experience mood changes or increased oestrogen symptoms (water retention, sensitive nipples) if their dose is too high. Regular blood tests monitor haematocrit, oestradiol, and other markers. Most side effects are manageable through dose adjustments, injection frequency changes, or ancillary medications. Serious side effects are rare when properly monitored.
Many doctors prescribe human chorionic gonadotropin (hCG) alongside TRT to maintain testicular function and fertility. Some patients require an aromatase inhibitor if oestrogen levels become too high, though this is less common with proper dosing. Regular blood tests determine if additional medications are needed. Avoid self-prescribing ancillary drugs—work with your doctor to optimise your protocol based on blood work and symptoms.
Testosterone cream can be very effective, especially scrotal cream which absorbs up to 50% compared to 10% for regular skin application. Cream produces higher DHT levels, which some men find beneficial for libido. However, cream requires daily application and careful timing of blood tests. It’s an excellent option for those uncomfortable with needles or requiring very stable daily dosing. Absorption varies between individuals, so close monitoring is necessary initially.
Blood Test Timing
Proper blood test timing is crucial for accurate testosterone level assessment and dose adjustments. Testing at the wrong time can show artificially high or low levels, leading to inappropriate dose changes.
| Testosterone Type | Injection Frequency | When to Test | Reason |
|---|---|---|---|
| Cypionate/Enanthate | Every 3-7 days | Trough (just before next injection) | Shows your lowest level; helps determine if dose is adequate |
| Sustanon | Every 5-7 days | Day of next injection (trough) | Most reliable reading despite mixed esters |
| Propionate | Daily or EOD | Morning before injection | Captures baseline after daily dosing reaches steady state |
| Cream (once daily) | Daily | 12-24 hours after last application | Before next application; timing window is narrow |
| Cream (twice daily) | Twice daily | 12 hours after last application | Midpoint between doses for accurate average |
Always test at the same time of day and same point in your injection cycle for consistent comparison. Morning tests (before 10am) are preferred as testosterone has natural circadian variation. Your doctor will want to see total testosterone, free testosterone, SHBG, oestradiol, and haematocrit at minimum.
Troubleshooting Common Issues
High Oestrogen Symptoms
If you experience water retention, emotional sensitivity, or gynaecomastia (breast tissue growth), your oestrogen may be elevated. This often occurs with high doses or infrequent injections causing testosterone spikes. Solutions include reducing your dose, increasing injection frequency, or adding a small amount of an aromatase inhibitor if necessary.
High Haematocrit
Testosterone increases red blood cell production. Haematocrit above 52% increases blood thickness and cardiovascular risk. Solutions include donating blood regularly, staying well-hydrated, reducing your dose, or switching from IM to SubQ injections which some studies suggest produces lower haematocrit increases.
Persistent Low Symptoms
If you still feel poorly despite testosterone levels in the normal range, consider other factors: thyroid function, vitamin D deficiency, poor sleep, high stress, or inadequate nutrition. Some men need higher testosterone levels than others to feel optimal. Work with your doctor to investigate all potential causes and adjust your protocol systematically.
Injection Site Reactions
Pain, swelling, or lumps at injection sites can occur. For IM injections, try different sites, ensure proper injection technique, and warm the testosterone to room temperature before injecting. For SubQ lumps, massage the area after injection, inject smaller volumes more frequently, or switch to IM administration.
References
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- Ramasamy R, Armstrong JM, Lipshultz LI. Preserving fertility in the hypogonadal patient: an update. Asian Journal of Andrology. 2015;17(2):197-200. doi:10.4103/1008-682X.142772
- Pastuszak AW, Gomez LP, Scovell JM, et al. Comparison of the effects of testosterone gels, injections, and pellets on serum hormones, erythrocytosis, lipids, and prostate-specific antigen. Sexual Medicine. 2015;3(3):165-173. doi:10.1002/sm2.76
- Morgentaler A, Zitzmann M, Traish AM, et al. Fundamental concepts regarding testosterone deficiency and treatment: International Expert Consensus Resolutions. Mayo Clinic Proceedings. 2016;91(7):881-896. doi:10.1016/j.mayocp.2016.04.007
- Patel AS, Leong JY, Ramos L, Ramasamy R. Testosterone is a contraceptive and should not be used in men who desire fertility. World Journal of Men’s Health. 2019;37(1):45-54. doi:10.5534/wjmh.180036
- Kovac JR, Pastuszak AW, Lamb DJ, Lipshultz LI. Testosterone supplementation therapy in the treatment of patients with metabolic syndrome. Postgraduate Medicine. 2014;126(7):149-156. doi:10.3810/pgm.2014.11.2843
- Bassil N, Alkaade S, Morley JE. The benefits and risks of testosterone replacement therapy: a review. Therapeutics and Clinical Risk Management. 2009;5:427-448. doi:10.2147/tcrm.s3025