RAD-140, LGD-4033 and MK-677 — Complete UK SARMs Guide 2026

Published: June 2026  ·  Category: Guides  ·  9 min read

RAD-140, LGD-4033 and MK-677 are the three most widely used compounds in the SARMs category among UK performance athletes and bodybuilders. Each operates through a different mechanism, each produces a different primary effect, and understanding the distinction between them is essential before deciding which to use, how to dose it, and whether to stack them. This guide covers each compound individually in plain terms — what it does, what the research says, what doses produce what results, and what side effects to be aware of — followed by the most practical stacking options for UK buyers.

All three compounds are available from the Intex Pharma SARMs and peptides range, independently tested by Janoshik Analytical with Certificates of Analysis in the product gallery before you order.

Shop Intex Pharma SARMs range

---

What SARMs are and how they differ from steroids

Selective Androgen Receptor Modulators are a class of investigational compounds designed to bind androgen receptors with tissue selectivity — stimulating anabolic effects in muscle and bone while theoretically limiting androgenic effects in organs such as the prostate and liver. According to the NIH's LiverTox database, the most studied SARMs include Ligandrol (LGD-4033), Enobosarm (Ostarine) and Vosilasarm (RAD-140). In experimental models, these agents were shown to increase lean body mass and promote muscle growth with fewer androgenic effects than traditional testosterone.

The key practical differences between SARMs and anabolic steroids for UK users are as follows. SARMs are orally active — no injection is required. They are more tissue-selective than traditional androgens, producing less impact on the prostate and liver at typical doses. However, they still suppress natural testosterone production to varying degrees, which means PCT is required after most SARMs cycles. They remain unapproved by the FDA and MHRA for human use and are sold as research compounds.

It is also important to note that MK-677 is not technically a SARM at all. It is a growth hormone secretagogue — a compound that stimulates the pituitary gland to release more natural growth hormone. It is grouped alongside SARMs in the performance community due to complementary effects and common stacking, but its mechanism is entirely different and it does not suppress the HPTA.

---

RAD-140 (Testolone) — the most potent muscle-building SARM

What RAD-140 does

RAD-140, developed by Radius Health Inc. as a potential treatment for breast cancer and muscle wasting, binds selectively to androgen receptors in muscle tissue and promotes protein synthesis and muscle growth with high anabolic activity and relatively low androgenic impact. According to Muscle and Brawn's RAD-140 research guide, Testolone primarily increases lean muscle tissue by enhancing testosterone and human growth hormone production, and may also increase training energy and strength while supporting fat loss. It is considered one of the strongest SARMs for muscle-building effects and produces dry, dense gains rather than the water-laden size associated with compounds like Dianabol.

RAD-140 dosing for UK users

UK SARMs' RAD-140 cycle guide recommends beginners start at 4 to 10mg daily, giving the body time to gauge response before increasing the dose. Intermediate users typically run 10 to 20mg daily. Doses above 20mg per day increase the risk of hormonal imbalances and liver enzyme elevation without proportionate benefit. Cycle length is 8 to 12 weeks. RAD-140 is orally active — no injection required. Take as a single daily dose in the morning for consistency.

RAD-140 side effects and health considerations

RAD-140 suppresses natural testosterone production. PCT is required after every cycle. The NIH LiverTox database documents case reports of liver toxicity associated with RAD-140, including elevated ALT and AST enzymes. Regular liver function blood panels are essential during any RAD-140 cycle. Furthermore, a phase 1 clinical study of RAD-140 in breast cancer patients documented liver enzyme elevations in a significant proportion of subjects, which reinforces the need for bloodwork monitoring even at conservative research doses. Aggression, mood changes and mild hair thinning in genetically predisposed users have also been reported.

---

LGD-4033 (Ligandrol) — the strongest lean mass SARM

What LGD-4033 does

LGD-4033, also known as Ligandrol or VK-5211, binds strongly to androgen receptors in muscle tissue and is regarded as the most effective SARM for lean muscle mass gains in the category. As a comprehensive SARMs guide explains, LGD-4033 encompasses an impressive anabolic-to-androgenic ratio that promotes muscle growth without virilisation — making it genuinely useful in both male and female research contexts. It is popular during bulking and lean mass cycles where the primary goal is quality muscle accumulation rather than cutting or conditioning.

A published case report in Experimental Physiology documented that LGD-4033 and MK-677 use in combination impacted body composition, circulating biomarkers and skeletal muscle androgenic hormone content — confirming measurable physiological changes at the doses typically used in the UK performance community.

LGD-4033 dosing for UK users

Standard LGD-4033 dosing for male users is 5 to 10mg daily for 8 to 12 weeks. Beginners should start at 5mg to assess response. At 10mg, the lean mass gains are meaningful and the compound produces noticeable results within two to three weeks. Women should use no more than 5mg daily due to LGD-4033's stronger androgenic profile compared to Ostarine. Take as a single daily dose. Cycle with the Intex Pharma SARMs range for third-party verified quality.

LGD-4033 side effects and health considerations

LGD-4033 is one of the more suppressive SARMs. Natural testosterone suppression is significant at 10mg and PCT is required after every cycle. The NIH's liver toxicity database documents a case of prolonged jaundice in a 52-year-old man following use of a product containing both RAD-140 and LGD-4033, resulting in biopsy-confirmed canalicular cholestasis. This case reinforces the importance of liver function monitoring with both compounds. Lipid profile changes — reduced HDL — are also documented. Standard bloodwork panels covering liver enzymes, lipids and testosterone should be run pre-cycle, mid-cycle and four weeks after PCT.

---

MK-677 (Ibutamoren) — GH secretagogue, not a SARM

What MK-677 does

MK-677 is not a SARM. It is a ghrelin receptor agonist — a growth hormone secretagogue that stimulates the pituitary gland to release more natural growth hormone, which in turn elevates IGF-1 levels. Muscle and Brawn's research guide distinguishes MK-677 clearly from SARMs: it does not bind to androgen receptors and therefore does not carry the same suppression risk or require PCT. Its effects come through elevated GH and IGF-1 rather than direct androgen receptor activation.

The practical effects of MK-677 are similar to those of low-dose exogenous HGH — improved sleep quality, enhanced recovery, increased muscle fullness, improved skin quality and gradual body composition improvements over weeks and months. Unlike injectable HGH, it stimulates the body's own pituitary output rather than introducing exogenous hormone, making it considerably more convenient and accessible for UK users.

MK-677 dosing for UK users

Standard MK-677 dosing is 10 to 25mg daily. The 2026 SARMs dosage research chart from Muscle and Brawn documents the studied dose range as 15 to 20mg per day. Most UK users start at 10mg and assess appetite stimulation and water retention before increasing. MK-677 can be run continuously for several months — because it does not suppress the HPTA, there is no mandatory cycle length in the way there is with suppressive SARMs. Take in the evening due to its appetite-stimulating effect through ghrelin receptor activity — taking it before bed minimises the impact on daytime appetite management and takes advantage of the GH pulse that occurs during sleep.

MK-677 side effects and health considerations

The most common MK-677 side effects are increased appetite — often dramatically — and water retention in the first four to six weeks. Mild lethargy is reported by some users, particularly those taking it in the morning. Insulin resistance and elevated blood glucose can occur at higher doses, similar to exogenous HGH, so fasting glucose monitoring is advisable particularly for users running MK-677 long-term. No PCT is required after MK-677 cessation as it does not suppress the HPTA.

---

Best RAD-140, LGD-4033 and MK-677 stacks for UK users

Stack 1 — RAD-140 and MK-677 (lean mass and recovery)

RAD-140 handles the anabolic component — driving lean muscle gains and strength — while MK-677 supports recovery, sleep quality and IGF-1 elevation. Research on RAD-140 and MK-677 stacking confirms that the two compounds complement each other well — RAD-140 promoting muscle growth directly through androgen receptors, MK-677 amplifying recovery and GH-driven anabolism through a completely separate pathway.

Stack 2 — LGD-4033 and MK-677 (bulking and mass)

This is one of the most effective combinations for pure lean mass gain. LGD-4033 provides the strongest direct anabolic stimulus of any SARM, while MK-677 adds the growth hormone and IGF-1 elevation that maximises protein synthesis and muscle repair between training sessions. The combination is particularly popular among UK users who want meaningful mass results without the side effect profile and PCT complexity of testosterone-based steroid cycles.

Stack 3 — RAD-140, LGD-4033 and MK-677 (advanced recomposition)

This stack combines all three pathways — direct androgen receptor activation via RAD-140, stronger anabolic SARM stimulation via LGD-4033, and GH/IGF-1 elevation via MK-677. It is suitable only for experienced users who have run each compound individually and understand their personal response to both RAD-140 and LGD-4033 before combining them. Both RAD-140 and LGD-4033 are suppressive compounds; stacking them requires robust PCT and thorough bloodwork monitoring.

---

Bloodwork — what to monitor on a SARMs cycle

Bloodwork is non-negotiable on any suppressive SARMs cycle. RAD-140 and LGD-4033 both suppress the HPTA and both carry documented liver enzyme elevation risk. The following panels should be run at minimum.

• Pre-cycle baseline. Total testosterone, free testosterone, LH, FSH, liver function (ALT, AST), lipids (HDL, LDL), full blood count and fasting glucose.
• Mid-cycle at week four to six. Liver function is the priority — ALT and AST elevation is the earliest indicator of hepatotoxic stress. Total testosterone to assess suppression degree. Fasting glucose if running MK-677. If liver enzymes are significantly elevated, stop immediately and allow them to normalise before proceeding.
• Four weeks after PCT. Total testosterone, LH and FSH to confirm HPTA recovery. If testosterone remains suppressed, seek guidance from a UK hormone specialist. Harley Street MD provides medically supervised PCT support for UK users requiring professional oversight.

---

Why product purity matters with RAD-140, LGD-4033 and MK-677

SARMs are among the most frequently adulterated and mislabelled compounds in the UK research chemical market. Products sold as RAD-140 have tested as entirely different compounds. Underdosed LGD-4033 is common enough to be a near-standard problem from low-tier sources. And because SARMs are orally active at very low doses, the margin for error in concentration is narrow — 5mg versus 10mg represents a completely different physiological impact.

Every product in the Intex Pharma SARMs and peptides range is independently tested by Janoshik Analytical using HPLC and mass spectrometry, confirming identity, purity and concentration. The Certificate of Analysis for every batch is available in the product gallery on the official Intex Pharma UK store before you order. You can verify the result directly on Janoshik's own website using the key on the COA. If you have any question about a product's authenticity or want to verify a batch number, contact us on WhatsApp at +44 7882 742370.

---