If you've been told you need testosterone replacement therapy and you've started looking into what the protocol actually involves, you'll quickly notice there are several injectable options sitting in front of you. The two most common IM depot choices in NZ are testosterone cypionate (brand: Depo-Testosterone) and Sustanon (a mix of four testosterone esters). Add Reandron (long-acting undecanoate) and the funded testosterone gel that was added to the Pharmaceutical Schedule in April 2024, and you have four genuinely different shapes of treatment to pick from.
Good news for cost: all four are fully funded by Pharmac for men who meet the clinical criteria for testosterone deficiency. Bad news for clarity: most NZ GPs only ever prescribe one or two of them, so which one you end up on can come down to who's prescribing rather than which is best for your situation.
This is a practical NZ guide to the two depot injection options — cypionate and Sustanon — what they actually are, how they differ, and how to think about which one suits you.
The four NZ-funded options at a glance
| Formulation | Type | Interval | Funded |
|---|---|---|---|
| Testosterone gel (e.g. Testogel) | Daily transdermal | Daily | ✅ Fully funded (since April 2024) |
| Testosterone cypionate (Depo-Testosterone) | IM depot, single ester | Every 2–4 weeks | ✅ Fully funded |
| Sustanon (mixed esters) | IM depot, four esters | Every 3 weeks | ✅ Fully funded |
| Testosterone undecanoate (Reandron) | IM depot, long-acting | Every 10–14 weeks | ✅ Fully funded |
BPAC NZ's 2024 guidance on prescribing testosterone in ageing men recommends starting with testosterone gel as first-line — it allows easy dose modification and rapid withdrawal if needed. Most NZ men who progress to long-term TRT eventually move to an injectable for the practicality (no daily application, no transfer-to-partner risk), and the depot choice is what this article is about.
Testosterone cypionate
What it is
Cypionate is a single testosterone ester — pure testosterone bound to the cypionate fatty-acid tail. The longer the tail, the slower the testosterone is released from the muscle into the bloodstream. Cypionate has a serum half-life of around 8 days.
Funded dose and interval
NZF lists the funded community dose as 50–400 mg every 2–4 weeks by deep intramuscular injection. Most NZ patients on funded Depo-Testosterone are on 200–250 mg every 2–3 weeks, given through their GP or a nurse-administered injection at the practice.
Internationally and in private practice (including at Enhanced Men) the trend is toward smaller, more frequent doses — typically 75–150 mg weekly or 150–250 mg fortnightly, often self-administered. The reason is curve shape: a smaller, more frequent dose produces a much flatter testosterone curve, which most patients find translates to steadier mood, libido, energy and bloodwork. Funding doesn't change between "monthly clinic injection" and "weekly self-injection" — it's the same drug at the same total dose, given more often.
Once it's in you
Cypionate is just testosterone. Your body has no way to know it came from an injection — the receptor response, symptom improvement, side-effect profile and bloodwork are identical to endogenous testosterone at that level. The trial-and-error is about getting the level right for you, not about the drug doing something exotic.
Sustanon
What it is
Sustanon is a mix of four testosterone esters combined in a single oily solution:
- Testosterone propionate (30 mg) — very short-acting, half-life ~1 day
- Testosterone phenylpropionate (60 mg) — short-acting, half-life ~2 days
- Testosterone isocaproate (60 mg) — intermediate, half-life ~4 days
- Testosterone decanoate (100 mg) — long-acting, half-life ~7 days
Total: 250 mg of testosterone esters per 1 mL ampoule.
The mix was designed in the 1970s to give a fast onset (the propionate gets to work within days) followed by a prolonged tail (the decanoate holds levels up for weeks) — without the need for two separate injections. In practice it produces a sharper peak in the first week and a steeper decline by week 3.
Funded dose and interval
NZF and Medsafe datasheet list the standard dose as 250 mg every 3 weeks by deep IM injection. Some men do well on this; others find the peak-to-trough cycling pronounced — feeling great for the first 10 days and noticeably flat by day 18–21. For those patients, splitting the dose (125 mg every 10–11 days) gives a flatter curve, again at the same total dose.
Where Sustanon shines, and where it doesn't
- Shines: Reliable, well-tolerated, decades of NZ prescribing experience, easy to obtain at any community pharmacy. If your GP is comfortable prescribing TRT, Sustanon is the most common option they'll reach for.
- Doesn't: The 3-week interval makes for a more pronounced level cycle than weekly cypionate. Some men find this cycling produces the same "great week / flat week" pattern they were trying to escape.
Cypionate vs Sustanon — side by side
| Cypionate | Sustanon | |
|---|---|---|
| Ester(s) | Single (cypionate) | Four (propionate, phenylpropionate, isocaproate, decanoate) |
| Standard NZ dose | 200–250 mg every 2–4 weeks | 250 mg every 3 weeks |
| Curve shape | Smoother on weekly/fortnightly dosing | Sharper peak day 2–7, fall-off by week 3 |
| Onset of action | 1–2 weeks | Within days (propionate component) |
| Self-administration | Common internationally, growing in NZ | Less common — usually given at the practice |
| Funded? | Yes | Yes |
| What it's best for | Steadier subjective levels, finer titration | Set-and-forget, well-established GP pathway |
Neither is "better." They're different tools for different patients. The choice usually comes down to:
- How much subjective level steadiness matters to you. If you don't want to feel a cycle, cypionate at weekly or fortnightly intervals usually wins.
- Whether you're going to self-inject. Self-administered TRT skews toward cypionate (or enanthate where available); clinic-administered toward Sustanon or Reandron.
- What your prescribing doctor is most comfortable managing. Both are funded; this often decides which one you actually get.
How dose is set
A starting dose isn't a forever dose. The maintenance dose is set by:
- Trough testosterone — drawn just before the next injection. Target: lower half to mid normal reference range (around 12–25 nmol/L, depending on symptoms and age).
- Free testosterone — often more clinically meaningful than total. Calculated from total + SHBG.
- Symptoms — energy, libido, morning erections, sleep, cognitive clarity, training response.
- Side effects — haematocrit (most important), oestradiol, blood pressure, mood.
Two men starting on the same dose can land at maintenance doses of 80 mg and 200 mg weekly respectively, both feeling great, both with bloods inside target. The dose is yours, not the formulation's default.
Injection route — IM or subcutaneous?
The old textbook says deep intramuscular into the gluteus or vastus lateralis with a 21–23 gauge needle. That's how almost all NZ-funded TRT is given in general practice.
Subcutaneous (SC) injection — into the abdominal or thigh fat layer with a 29–30 gauge insulin syringe — works as well for cypionate and is much easier to self-administer. Studies (mostly international) show comparable serum levels with SC, sometimes slightly lower haematocrit response, and dramatically better patient adherence. For men who want to self-inject weekly, SC is the practical default.
Sustanon is less well-studied SC, partly because of its higher injection volume (1 mL ampoule) and the propionate component (which can sting more SC). It's most often given IM.
What to monitor
A reasonable starter monitoring protocol — the same whether you're on cypionate or Sustanon:
- Baseline (pre-treatment): Full hormone panel (total + free testosterone, SHBG, LH, FSH, prolactin, oestradiol), FBC, lipids, liver function, HbA1c, PSA (if 40+), ferritin
- Week 6–8: Trough total testosterone, oestradiol, FBC (catch any haematocrit rise early)
- Month 3: Full repeat of baseline panel
- Month 6: Repeat; first dose review if needed
- Annually thereafter: Full panel, PSA, blood pressure
The single most-watched number is haematocrit. All TRT increases red cell production. If yours climbs above the threshold, we adjust dose, increase hydration, and arrange venesection through NZ Blood Service if needed. Same pattern for both formulations.
Cost in NZ
For both cypionate and Sustanon, the drug itself is fully Pharmac-funded for men who meet the standard criteria — you fill the script at any community pharmacy on the standard NZ pathway. Reviews, longer consults, comprehensive bloodwork and self-injection training (the Enhanced Men service) are charged separately for the consult time — what you pay for is depth of clinical management, not the medicine.
What we do at Enhanced Men
We prescribe testosterone cypionate as our standard depot TRT — typically weekly or fortnightly subcutaneous self-injection at 75–150 mg per week. Cypionate at this frequency gives the flattest curve and the fastest dose titration if your bloodwork moves.
We're not against Sustanon, Reandron or the funded gel — they're all good drugs and we'll happily continue managing you on any of them if that's what you're already on. The case for cypionate at our protocol is curve steadiness and titration speed, not drug superiority.
FAQ
Is cypionate / Sustanon the same as the steroids people use for bodybuilding? The molecule is the same testosterone, yes. The dose, monitoring and intent are completely different. TRT brings a deficient man back into the normal physiological range under monitoring. Performance-use cycles push levels several times above normal without monitoring — that's a different drug pattern with different risks. The drug itself isn't dangerous; unmonitored super-physiological dosing is.
Can I switch from Sustanon to cypionate (or vice versa)? Yes. The switch is straightforward — stop one, start the other, re-check bloods at 6–8 weeks on the new protocol. Most patients who switch from 3-weekly Sustanon to weekly cypionate report a smoother subjective experience within 4–6 weeks.
Do I have to inject myself? No. The funded NZ pathway typically uses clinic-administered injections — your practice nurse or GP gives them. Self-injection is an option (and what most international protocols default to for weekly/fortnightly cypionate) but you can absolutely do TRT without ever touching a needle yourself.
Does it matter what time of day I inject? Not really. Depot esters release over days to weeks. Pick a day of the week you'll remember and stick to it.
What about testicular shrinkage and fertility? All TRT suppresses your own testosterone production by shutting down the pituitary signal. Testicles shrink. Fertility drops, often to zero on therapy. Both are reversible after stopping in most men but take 6–18 months. If you're planning children in the next 1–2 years, talk to us before starting — there are protocols (HCG, FSH analogues) that preserve fertility on therapy.
Can I drink alcohol on TRT? Yes, in normal moderation. Heavy chronic alcohol affects testosterone and liver — its own problem — but a couple of beers won't affect your protocol.
References (NZ-specific)
- BPAC NZ — Prescribing testosterone in ageing males (2024)
- New Zealand Formulary — testosterone esters monograph (nzf.org.nz)
- Pharmac — Pharmac to fully fund testosterone gel for all who need it (Feb 2024)
- Medsafe NZ — Depo-Testosterone data sheet
- Medsafe NZ — Sustanon data sheet
- Endocrine Society — Testosterone Therapy in Men with Hypogonadism: Clinical Practice Guideline
This article is general health information and does not replace personalised medical advice. TRT is a long-term treatment with real benefits and real risks; the decision to start, and which formulation to use, should be made with a doctor who knows your full picture.