Sustanon in the UK: what's in it, how it behaves and who it suits

Sustanon has the best marketing of any testosterone in Britain, and as far as I know it's never run a single advert. Four esters! Fast and slow release in one jab. Ask about it in any gym changing room and someone will tell you it's the good stuff.

I don't dislike Sustanon. It's a licensed UK medicine that's been around for decades. But the reputation and the reality are two different things, so this is my plain account of Sustanon in the UK: what's actually in the ampoule, why levels on it go up and down the way they do, how you get it legally, who I think it suits, and why we usually reach for something else here.

What's actually in the ampoule

Sustanon 250 is a 1 ml ampoule of oil containing four different testosterone esters. An ester is a fatty chain bolted onto the testosterone molecule so it seeps out of the muscle slowly instead of being gone within the hour. Different chain lengths, different speeds.

According to the product information, each 1 ml contains:

• Testosterone propionate, 30 mg. The quick one.
• Testosterone phenylpropionate, 60 mg. Also fairly quick.
• Testosterone isocaproate, 60 mg. Somewhere in the middle.
• Testosterone decanoate, 100 mg. The slow one, and the biggest share.

Add those up and you get 250 mg, which is where the name comes from. Here's a nerdy one, though. That 250 mg is the weight of the esters, and the fatty chains weigh something. The actual testosterone in the ampoule is about 176 mg. Worth knowing when people compare products milligram for milligram.

The other thing on the label that matters: the oil is arachis oil, which is peanut oil. The product information says Sustanon shouldn't be used by anyone allergic to peanuts or soya. If that's you, tell your prescriber, because it rules this one out completely.

It's licensed in the UK for testosterone replacement in men with hypogonadism (testicles not making enough testosterone, or the brain not telling them to), and it's given as a deep injection into a muscle. The UK licence is held by Aspen.

Four esters, one rollercoaster

The original idea was clever. The short esters get your levels up quickly, the long ones keep them there, and one injection covers several weeks. The licensed schedule reflects that: usually 1 ml every three weeks.

In practice it doesn't flatten out the way the theory promises. The product information describes testosterone peaking a day or two after an injection, well above the normal range, then sliding back down to the bottom of the normal range at around three weeks. So on the licensed schedule you get a big high at the start and a low patch before the next dose.

That's the pattern behind the classic description of three-weekly Sustanon: great for the first week, fine for the second, flat and irritable by the third. Libido, mood and energy tend to follow the curve. And honestly? For a treatment whose whole point is to make you feel steady, that's a bit of an own goal.

High peaks have a second cost. The bigger the spike, the more testosterone gets converted to oestradiol (the main oestrogen in men), and the harder your bone marrow is pushed to make red cells. That shows up as a rising haematocrit, the measure of how thick your blood is, which is the side effect I spend the most time managing on any injectable.

Plenty of prescribers deal with this by giving smaller doses more often, weekly or every ten days. That's off-licence (outside the schedule in the product information), but it's a legitimate and common prescribing decision, and it does smooth things out. The catch is that once you're injecting weekly anyway, the main selling point of a four-ester blend has largely gone, and you've still got four release curves stacked on top of each other, which makes the numbers harder to read when you're adjusting a dose.

Sustanon vs the other options

I've compared all the UK esters properly in my post on enanthate, cypionate, Sustanon and Nebido, so I won't repeat it all. The short version, side by side:

All four deliver exactly the same hormone. What differs is the shape of your levels between doses, and how easily your doctor can adjust it against your bloods.

Getting Sustanon in the UK, legally

There are two legitimate routes, and they're both on prescription.

• The NHS. Sustanon is in the BNF and some GPs and endocrinologists still prescribe it, though many areas now favour Nebido or a gel. Getting there means meeting the NHS criteria first, which I've covered in TRT on the NHS.
• A private prescription. A registered doctor assesses you, confirms low testosterone on proper blood tests, and prescribes it, with a registered pharmacy dispensing it.

And then there's the third route, the one most of the search results are actually selling. Testosterone is a Class C controlled drug in the UK. On a prescription, completely legal. Supplying it without one is a criminal offence, so every site offering Sustanon 250 for sale without a consultation is operating outside the law, however professional the website looks.

Legality is the smaller problem. You don't know what's in the vial, or whether the dose on the label is the dose inside. The Medicines and Healthcare products Regulatory Agency (MHRA) regularly seizes illegally traded steroids. And nobody is checking your haematocrit, your PSA or your fertility while you take it.

Here's a quick test. There's no licensed Sustanon 300 (or 400, or 500) in the UK. The only licensed version here is Sustanon 250. If you've been offered a 300, it's come from somewhere that isn't a pharmacy.

Who I think it suits (and who it doesn't)

I'll be straight with you. At Arc we mainly prescribe enanthate and cypionate, for the reasons above: one release curve, small regular doses, easier to fine-tune. That's a preference, not a verdict on Sustanon.

Where Sustanon makes sense:

• A man who's already on it, feels well across the whole interval, and has stable bloods. If it isn't broken, I'm not going to break it.
• Someone who's tried other options and genuinely does better on it. It happens.

Where I'd think twice:

• A peanut or soya allergy. That's a hard no.
• A man whose main complaint is feeling up and down. Swapping to a single ester with smaller, more frequent doses often fixes that without changing the total amount.
• A haematocrit that already runs high. Big peaks don't help.
• Anyone who's chosen it because a forum said it's the strong one. It isn't stronger. It's testosterone.

Whatever the product, the rest of TRT doesn't change. Testosterone can switch off sperm production, so if a family is on the cards at any point, that's a conversation before you start (there's more in TRT and fertility). It can make sleep apnoea worse, nudge up blood pressure and raise PSA, the prostate marker. And BSSM guidance wants two early morning testosterone blood tests showing genuinely low levels before anyone is diagnosed. One bad reading isn't enough.

If you're already on Sustanon

A lot of men reading this will already have an ampoule in the fridge drawer. (Wrong place, by the way. The product information says store it below 25 degrees and don't refrigerate it.) A few things I'd want you to know.

Time your bloods. On any injection, when the sample is taken changes what it means. I like it just before the next injection, the trough, because that tells us whether the dose holds you up to the end. A sample taken two days after the jab mostly tells you about the spike.

Don't change the schedule yourself. Splitting an ampoule into smaller weekly doses is a prescribing decision, partly because Sustanon comes in single-use glass ampoules, not multi-dose vials. Once opened, it's meant to be used straight away. If you need help working out what volume a prescribed dose is, the TRT dosage calculator does the sums, but the dose itself comes from your prescriber.

Know where it goes. Sustanon is licensed as a deep injection into muscle. Some prescribers give testosterone under the skin, but that's outside Sustanon's licence. My post on where to inject testosterone covers the sites and the technique.

If the third week is grim, say so. That's not you being soft. It's pharmacology. If your current clinic shrugs, you can switch your TRT to us and bring your existing bloods, and we'll look at whether a different product or schedule would suit you better.

The bottom line

Sustanon is a perfectly respectable, licensed medicine with a gym reputation it didn't ask for. It isn't stronger than other testosterone, and on its licensed three-weekly schedule the peaks and troughs are real. Plenty of men are well on it. Others do better on something steadier.

If you're thinking about TRT, start with the diagnosis, not the product. Get tested properly, have the fertility chat, and let a doctor pick the medicine from your bloods. If you'd like us to do that, get started here, and what it costs is all on the pricing page.

The best testosterone, it turns out, is the one with a doctor reading your bloods.

Dr Chris Airey

Sources: Sustanon 250 solution for injection, Summary of Product Characteristics (Aspen), electronic Medicines Compendium. Hackett G et al, The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice, World Journal of Men's Health, 2023. Bhasin S et al, Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology and Metabolism, 2018. Misuse of Drugs Act 1971 and Misuse of Drugs Regulations 2001.

Keep reading

For the complete picture, my full guide to TRT in the UK covers eligibility, blood test thresholds, NHS and private routes, costs and monitoring. If you're weighing up products, read the esters compared next.