Sustanon 250 Injections: Uses, Dosage, and What to Expect

Sustanon 250 is one of the most widely prescribed testosterone preparations in the UK, particularly through the NHS. If your clinician has recommended Sustanon injections as part of testosterone replacement therapy (TRT), or if you are researching your options before starting treatment, understanding how this medication works will help you make an informed decision about your care.

This guide explains what Sustanon 250 is, how it differs from other testosterone formulations, what a typical dosing schedule looks like, and what you can realistically expect from treatment — including the side effects you should be aware of and the monitoring that responsible prescribing requires.

What Is Sustanon 250?

Sustanon 250 is an injectable testosterone preparation that contains a blend of four different testosterone esters dissolved in an arachis (peanut) oil carrier. It was originally developed by Organon in the 1970s with the intention of creating a formulation that would provide both rapid and sustained testosterone release from a single injection.

The four esters in each 1ml ampoule are:

Ester	Amount per ampoule	Approximate half-life	Role in the blend
Testosterone propionate	30 mg	0.8 days	Rapid onset — provides initial testosterone rise within hours
Testosterone phenylpropionate	60 mg	1.5 days	Short-to-medium acting — maintains levels in the first week
Testosterone isocaproate	60 mg	4 days	Medium acting — bridges the gap between fast and slow esters
Testosterone decanoate	100 mg	7.5 days	Long acting — sustains levels into the second and third week

Each ampoule delivers a total of 250 mg of testosterone across these four esters. The blend was designed so that once the fast-acting propionate begins to decline, the medium-acting esters take over, and finally the long-acting decanoate provides a sustained tail of testosterone release. In theory, this produces more stable blood levels than a single-ester preparation injected at the same frequency — though in practice, the picture is more nuanced, as we will discuss below.

How Do Sustanon Injections Work?

When Sustanon 250 is injected into a muscle (typically the gluteal muscle in the buttock or the vastus lateralis in the outer thigh), the oily solution forms a depot within the muscle tissue. The different testosterone esters are then gradually cleaved by enzymes called esterases, releasing free testosterone into the bloodstream at different rates.

The propionate ester is cleaved within hours, producing a noticeable rise in blood testosterone within the first day. The phenylpropionate and isocaproate esters sustain this over the following days. The decanoate ester continues releasing testosterone for roughly two weeks after injection.

This pharmacokinetic profile means that after a Sustanon injection, testosterone levels rise relatively quickly, peak within one to three days, and then gradually decline over the following two to three weeks. The rate of decline depends on individual metabolism, injection site, and the patient’s body composition.

Who Is Sustanon 250 Prescribed For?

Sustanon 250 is licensed in the UK for the treatment of testosterone deficiency (hypogonadism) in adult men. According to the Summary of Product Characteristics (SmPC), it is indicated where testosterone deficiency has been confirmed by clinical features and biochemical tests.

You may be prescribed Sustanon injections if:

• You have been diagnosed with primary hypogonadism (where the testes do not produce sufficient testosterone, due to conditions such as Klinefelter syndrome, orchidectomy, or testicular injury)
• You have secondary hypogonadism (where the pituitary gland or hypothalamus does not adequately stimulate testosterone production)
• You have age-related testosterone decline with significant symptoms that have been confirmed by blood testing
• Other forms of TRT (such as gels) have been tried and found unsuitable or ineffective

Sustanon is not appropriate for everyone. It is contraindicated in men with known or suspected prostate or breast cancer, in those with severe liver, kidney, or heart disease, and in men with a history of hypersensitivity to any of the active substances or excipients — including those with a peanut or soya allergy, as the carrier oil is arachis (peanut) oil.

Dosing Schedule: How Often Do You Inject Sustanon?

The standard prescribing information for Sustanon 250 recommends one injection of 1ml (250 mg) every three weeks. However, clinical practice has evolved considerably since this dosing recommendation was established, and many TRT specialists now consider the three-weekly protocol to be suboptimal for a significant proportion of patients.

Why the standard three-weekly protocol may not be ideal

With a three-weekly injection interval, many men experience a pattern commonly described as “peaks and troughs.” Testosterone levels rise sharply in the days following injection, often exceeding the upper end of the reference range, and then decline steadily over the following weeks. By the end of week three, levels can fall back below the lower reference range, resulting in a return of low testosterone symptoms such as fatigue, low mood, and reduced libido.

This rollercoaster effect is one of the most common complaints among men on Sustanon, and it is a legitimate clinical concern. The goal of TRT is to maintain testosterone within the physiological range consistently, not to cycle between supraphysiological peaks and hypogonadal troughs.

Modern dosing approaches

Many private TRT clinics in the UK, including our clinicians at Evernu, now favour more frequent, lower-volume Sustanon injections to improve blood level stability. Common alternative protocols include:

• Every two weeks: 1ml (250 mg) every 14 days — a simple adjustment that reduces the trough effect
• Weekly: 0.5ml (125 mg) every 7 days — provides significantly more stable blood levels
• Twice weekly: 0.25ml (62.5 mg) every 3.5 days — the most stable option for Sustanon, though it requires more frequent injections

Your clinician will determine the most appropriate dosing frequency based on your blood test results, symptom response, and personal preferences. If you are currently on a three-weekly protocol and experiencing significant peaks and troughs, it is worth discussing a more frequent dosing schedule with your prescriber.

How Is Sustanon 250 Administered?

Sustanon 250 is administered as an intramuscular injection. The most common injection sites are:

• Gluteal muscle (buttock): The upper outer quadrant is the standard site, offering a large muscle mass for comfortable injection
• Vastus lateralis (outer thigh): Preferred by many men who self-inject, as it is easier to reach without twisting
• Deltoid (upper arm): Sometimes used for smaller volumes, though less common for the full 1ml dose

The injection is typically given using a 21-gauge drawing needle (to draw the viscous oil from the ampoule) and a 23- to 25-gauge injection needle (1 to 1.5 inches in length). The oil-based carrier means the solution is thicker than water-based injections, so injecting slowly and steadily over 10 to 15 seconds helps minimise discomfort.

Some clinicians and patients now use subcutaneous injection for smaller Sustanon doses (such as the 0.25ml or 0.5ml volumes used in split-dose protocols). While Sustanon is licensed for intramuscular use only, there is growing clinical evidence supporting subcutaneous administration of testosterone preparations, and many TRT specialists consider it an acceptable off-label approach for appropriate patients.

Advantages of Sustanon Injections

• NHS availability: Sustanon 250 is widely available on the NHS and is the most commonly prescribed injectable testosterone in the UK, making it an accessible option for many men
• Low cost: At approximately £3 to £10 per ampoule, Sustanon is one of the most affordable TRT options
• Rapid onset: The propionate ester provides noticeable effects within one to two days of injection
• Flexible dosing: The 1ml ampoule can be split across multiple injections for more stable blood levels
• Proven track record: Sustanon has been used clinically for over 50 years, and its safety and efficacy profile is well established
• Self-injection: Once trained, most men can self-inject at home, reducing the need for clinic visits

Disadvantages of Sustanon Injections

• Peaks and troughs: When injected every three weeks as per the original prescribing recommendation, many men experience significant fluctuations in testosterone levels and corresponding symptoms
• Glass ampoules: Sustanon comes in single-use glass ampoules rather than multi-dose vials, which means any unused medication from a split dose must be stored carefully (and is technically off-label)
• Peanut oil carrier: The arachis oil base makes Sustanon unsuitable for men with peanut or soya allergies
• Injection site soreness: The oil-based formulation can cause more post-injection discomfort compared to water-based preparations
• Oestrogen conversion: The rapid testosterone peak following injection can lead to higher oestrogen conversion (aromatisation) in some men, potentially causing side effects such as fluid retention or gynaecomastia

Side Effects of Sustanon Injections

As with any form of testosterone replacement, Sustanon injections carry the potential for side effects. Most are manageable and dose-dependent, but awareness of what to watch for is important.

Common side effects

• Injection site pain, redness, or swelling
• Acne or oily skin, particularly in the first few months
• Mild fluid retention
• Increased body or facial hair growth
• Mood changes, including occasional irritability

Less common but clinically significant side effects

• Polycythaemia: An increase in red blood cell count (haematocrit) is one of the most important side effects to monitor. Elevated haematocrit increases blood viscosity and the risk of blood clots. Regular blood tests are essential, and dose adjustments may be needed if levels rise above the safe threshold
• Suppression of natural testosterone production: Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal (HPG) axis, reducing or halting natural testosterone and sperm production. This is an important consideration for men who may want to father children
• Changes in liver function: Although injectable testosterone is not associated with the hepatotoxicity seen with oral preparations, liver function should be monitored as part of routine TRT blood work
• Lipid changes: TRT can affect cholesterol profiles, and regular lipid monitoring is recommended
• Sleep apnoea: Testosterone therapy may worsen pre-existing obstructive sleep apnoea
• Prostate effects: While testosterone does not cause prostate cancer, it can stimulate the growth of existing prostate tissue. PSA (prostate-specific antigen) monitoring is a standard part of TRT follow-up

The NICE guidelines on hypogonadism recommend regular monitoring of haematocrit, PSA, liver function, and lipid profiles for all men on testosterone replacement therapy.

Monitoring Requirements on Sustanon

Responsible TRT prescribing requires ongoing blood monitoring. At Evernu, we follow evidence-based monitoring protocols aligned with British Society for Sexual Medicine (BSSM) and Endocrine Society guidelines. A typical monitoring schedule includes:

Timepoint	Tests
Baseline (before starting)	Total testosterone, free testosterone, SHBG, LH, FSH, full blood count, haematocrit, PSA, liver function, lipid profile, HbA1c, thyroid function
6–8 weeks after starting	Total testosterone (trough level), full blood count, haematocrit, oestradiol
3 months	Comprehensive blood panel including all baseline markers
6 months	Comprehensive blood panel
Ongoing (every 6–12 months)	Testosterone, full blood count, haematocrit, PSA, liver function, lipid profile

For Sustanon specifically, trough blood samples (taken immediately before the next injection is due) are the most useful for assessing whether dosing frequency is adequate. If your trough testosterone is below the reference range, your clinician may recommend increasing the injection frequency rather than the dose.

If you are not currently receiving regular blood monitoring as part of your TRT, this is a significant red flag. You can arrange a comprehensive testosterone blood test through Evernu to establish your baseline or check your current levels.

How Sustanon Compares to Other TRT Injections

Sustanon is not the only injectable testosterone option available in the UK. Understanding how it compares to other formulations can help you and your clinician select the most appropriate treatment.

Feature	Sustanon 250	Nebido (testosterone undecanoate)	Testosterone enanthate
Ester type	Four-ester blend	Single long-acting ester	Single medium-acting ester
Dose per injection	250 mg / 1ml	1000 mg / 4ml	Typically 125–250 mg
Standard injection frequency	Every 2–3 weeks	Every 10–14 weeks	Every 1–2 weeks
Self-injection	Yes (commonly)	Usually clinic-administered	Yes (commonly)
Blood level stability	Moderate (better with frequent dosing)	Good overall, may dip at end of cycle	Very good with weekly or twice-weekly dosing
NHS availability	Widely available	Available but less commonly prescribed due to cost	Less commonly prescribed on NHS
Approximate cost per injection	£3–£10	£80–£120	£20–£40
Carrier oil	Arachis (peanut) oil	Castor oil	Varies (often castor or sesame oil)

For a detailed comparison of all TRT injection options, including our guide to Nebido and testosterone enanthate, visit our blog for in-depth resources.

Sustanon vs Nebido

The main advantage of Nebido over Sustanon is injection frequency: four to five injections per year versus 12 to 52 (depending on your Sustanon protocol). However, Nebido requires a larger needle, a 4ml injection volume, and is typically administered by a healthcare professional rather than self-injected. It is also significantly more expensive. Men who prefer the convenience of infrequent injections and do not mind clinic visits may favour Nebido, while those who prefer self-injection and more flexible dosing tend to prefer Sustanon or enanthate.

Sustanon vs testosterone enanthate

Testosterone enanthate is a single-ester preparation that many private TRT clinicians now prefer over Sustanon. Its consistent half-life (approximately 4.5 days) produces more predictable pharmacokinetics than the multi-ester Sustanon blend, making dose titration simpler. When injected weekly or twice weekly, enanthate typically produces the most stable blood levels of any injectable testosterone. The trade-off is that enanthate is not as widely available on the NHS as Sustanon and is slightly more expensive per injection.

Availability of Sustanon 250 in the UK

Sustanon 250 is a prescription-only medicine (POM) in the UK and cannot be purchased over the counter. It is manufactured by Aspen Pharma and is available through:

• NHS prescription: Your GP or endocrinologist can prescribe Sustanon if you have a confirmed diagnosis of testosterone deficiency. NHS prescriptions are subject to standard prescription charges (currently £9.90 per item in England, free in Scotland, Wales, and Northern Ireland)
• Private prescription: Private TRT clinics, including Evernu, can prescribe Sustanon as part of a comprehensive TRT programme

It is important to note that purchasing Sustanon from unregulated online sources carries significant risks. Products may be counterfeit, contaminated, or incorrectly dosed. The MHRA regularly issues warnings about unlicensed testosterone products, and we strongly advise obtaining testosterone only through a regulated prescriber.

What to Expect When Starting Sustanon Injections

If you and your clinician have agreed that Sustanon is the right option for you, here is a general timeline of what to expect:

• Week 1–2: Most men notice an initial lift in energy and mood within the first few days, driven by the fast-acting propionate ester. Libido may also increase. These early effects are real but can be subtle
• Week 3–6: As your body adjusts to regular dosing, improvements in energy, mental clarity, and motivation tend to become more consistent. Sleep quality often improves during this period
• Month 2–3: Mood stabilisation becomes more apparent. You may notice early changes in body composition, particularly if you are exercising regularly. Sexual function improvements continue to develop
• Month 3–6: This is when the more significant physical changes typically emerge — improved muscle mass (with resistance training), reduced body fat, better exercise recovery, and more consistent energy throughout the day
• Month 6–12: Bone mineral density improvements, continued body composition changes, and metabolic benefits become more established. By this stage, your dosing protocol should be well optimised based on your blood work

Everyone responds differently to testosterone replacement, and some men notice dramatic improvements while others experience more gradual changes. Regular blood testing and clinical reviews are essential to ensure your protocol is optimised for you individually.

Practical Tips for Sustanon Injections

• Warm the ampoule: Holding the ampoule in your palm for a few minutes before injection warms the oil and makes it flow more easily, reducing injection time and discomfort
• Rotate injection sites: Alternating between left and right glutes or thighs helps prevent scar tissue build-up and reduces the likelihood of injection site reactions
• Use a separate drawing needle: Drawing the oil through a larger gauge needle and then switching to a finer injection needle preserves the sharpness of the injection needle and makes the injection more comfortable
• Inject slowly: Take 10 to 15 seconds to inject the full 1ml. Rushing the injection can increase post-injection soreness
• Apply pressure, not massage: After withdrawing the needle, apply gentle pressure with a cotton ball for 10 to 20 seconds. Avoid rubbing or massaging the site, as this can push oil back toward the surface and increase soreness

Is Sustanon Right for You?

Sustanon 250 remains a reliable and effective option for testosterone replacement therapy, particularly for men accessing TRT through the NHS or those looking for an affordable injectable option. Its main limitation — blood level fluctuations — can be largely mitigated by injecting more frequently at lower doses.

If you are unsure whether you have low testosterone, our free online testosterone assessment can help you understand whether further investigation is worthwhile. If you would like to check your testosterone levels with a comprehensive blood panel, you can order a testosterone blood test through Evernu.

For men already diagnosed with low testosterone and looking for expert-guided TRT with thorough monitoring, our testosterone replacement therapy service provides personalised protocols, regular blood work, and ongoing clinical support from qualified prescribers.

This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting or changing any medication. Evernu is regulated by the Regulation and Quality Improvement Authority (RQIA).