Weight Loss

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Loss of Muscle Mass: Causes and Treatments

Written by

Bolt Pharmacy

Published

1/11/2026

Last Updated

1/11/2026

Overseen by Marie Boes

Clinical oversight Adedayo Titiloye, Deputy Superintendent Pharmacist, GPhC 2072783

Checked against the Bolt Clinical Accuracy Standard, 1 November 2026

Loss of muscle mass is a common and clinically significant problem that affects people of all ages, though it becomes increasingly prevalent after the age of sixty. Whether driven by ageing, chronic illness, inactivity, or poor nutrition, muscle loss can reduce independence, increase the risk of falls, and worsen outcomes from other health conditions. Understanding the causes, how it is diagnosed, and what can be done to slow or reverse it is essential for anyone concerned about their strength, mobility, or long-term health. This article covers the key facts, UK-relevant guidance, and practical steps you can take.

Summary: Loss of muscle mass occurs when muscle protein breakdown exceeds rebuilding, driven by ageing, inactivity, poor nutrition, or underlying illness, and can be slowed or partially reversed with resistance exercise and adequate protein intake.

Age-related muscle loss (sarcopenia) typically begins in a person's thirties and accelerates after sixty, with adults losing an estimated 3 to 8 per cent of muscle mass per decade after middle age.
Diagnosis in the UK follows EWGSOP2 criteria, combining grip strength, gait speed, and body composition measurements such as DEXA or bioelectrical impedance analysis.
No medicine is currently licensed in the UK specifically for sarcopenia; treatment centres on resistance exercise, adequate dietary protein, and management of any underlying condition.
GLP-1 and dual GIP/GLP-1 receptor agonists (semaglutide, tirzepatide) can cause gastrointestinal side effects and require monitoring for pancreatitis, gallbladder disease, and hypoglycaemia when combined with insulin or sulfonylureas.
Resistance training on at least two days per week, combined with protein spread across meals, produces the greatest gains in muscle mass and function, including in frail older adults.
Unexplained progressive weakness, unintentional weight loss exceeding 5 per cent of body weight, or frequent falls warrant prompt GP assessment to exclude an underlying medical cause.

What causes loss of muscle mass and who is most at risk?
How do doctors in the UK diagnose and measure muscle loss?
Which treatments and medicines can help rebuild muscle mass?
What side effects and safety concerns should you know about?
Can diet and exercise really reverse muscle loss?
When should you see a GP about losing muscle mass?
Scientific References
Frequently Asked Questions

Condition / Process	Primary Cause	Key Risk Groups	Main Diagnostic Tools	First-Line Interventions
Sarcopenia	Age-related decline in muscle protein synthesis, falling testosterone and oestrogen	Adults over 65, estimated 3 to 8 per cent muscle loss per decade	Grip strength, gait speed, SPPB, DEXA scan	Resistance exercise at least twice weekly, increased dietary protein
Cachexia	Systemic inflammation and disease-driven catabolism, for example cancer or heart failure	People with cancer, heart failure, or chronic inflammatory conditions	CRP, ESR, serum albumin, full blood count	Treat underlying disease, oral nutritional supplements per NICE CG32
Disuse atrophy	Prolonged immobility or inactivity reducing mechanical load on muscle fibres	Post-surgical or hospitalised patients, those with limited mobility	Clinical assessment, functional tests, BIA	Graded mobilisation, physiotherapy-led resistance exercise
Corticosteroid-induced wasting	Long-term corticosteroid use promoting muscle catabolism	People on long-term steroids for inflammatory conditions such as COPD or rheumatoid arthritis	Clinical history, creatine kinase, muscle function assessment	Use lowest effective steroid dose, resistance training, adequate protein
Endocrine-related muscle loss	Hyperthyroidism, Cushing's syndrome, or hypogonadism disrupting anabolic signalling	People with endocrine disorders, postmenopausal women, men with confirmed hypogonadism	Thyroid function tests, HbA1c, hormone levels	Treat underlying endocrine disorder; testosterone or HRT where clinically indicated
Malnutrition-related wasting	Insufficient dietary protein and micronutrients, including vitamin D deficiency	Older hospital inpatients, those on very restrictive diets, people with malabsorption	Serum albumin, vitamin D, vitamin B12, folate, dietitian assessment	High-protein diet, NHS-prescribed oral nutritional supplements, vitamin D supplementation per SACN
Obesity or type 2 diabetes-associated loss	Metabolic dysfunction and systemic inflammation reducing lean mass relative to fat mass	People with obesity or type 2 diabetes, particularly during rapid weight loss	HbA1c, body composition via DEXA or BIA, clinical review	Resistance training and adequate protein alongside any weight-management medicine such as tirzepatide or semaglutide

What causes loss of muscle mass and who is most at risk?

Loss of muscle mass is caused by ageing, inactivity, poor nutrition, and systemic illness; older adults, people with chronic conditions such as cancer or heart failure, and those on long-term corticosteroids are at greatest risk.

Loss of muscle mass occurs when the body breaks down muscle protein faster than it can rebuild it, a process driven by ageing, inactivity, poor nutrition, and underlying illness. The medical term for age-related muscle loss is sarcopenia, which typically begins in a person's thirties and accelerates after the age of sixty.^[1] Hormonal changes, including declining testosterone and oestrogen levels, reduce the signals that stimulate muscle protein synthesis, making older adults particularly vulnerable.

It is useful to distinguish three overlapping processes: sarcopenia (age-related loss of muscle mass and function), cachexia (muscle wasting driven by systemic disease and inflammation, for example in cancer or heart failure), and disuse atrophy (loss resulting from immobility or inactivity). Treatment approaches differ considerably depending on which process predominates.

Several groups face a heightened risk:

Older adults, especially those over sixty-five, who lose an estimated 3 to 8 per cent of muscle mass per decade after middle age, according to figures cited in the EWGSOP2 consensus on sarcopenia (Cruz-Jentoft et al., Age and Ageing, 2019)
People with chronic conditions such as type 2 diabetes, chronic kidney disease, heart failure, or cancer, where systemic inflammation accelerates muscle breakdown
Those with prolonged immobility, including patients recovering from surgery or hospitalisation
Individuals with poor dietary protein intake, including some older adults and those following very restrictive diets
People using certain medicines long-term, including corticosteroids, which promote muscle catabolism
People with endocrine disorders such as hyperthyroidism or Cushing's syndrome, or with conditions causing malabsorption, which can accelerate muscle loss through distinct mechanisms

Malnutrition is a significant contributing factor in the UK. BAPEN data and NICE guidance on nutrition support in adults (CG32) indicate that malnutrition affects a substantial proportion of older hospital inpatients, compounding muscle loss during periods of illness.^[2] Inflammatory conditions such as rheumatoid arthritis and chronic obstructive pulmonary disease (COPD) also accelerate the process through elevated levels of cytokines that promote protein breakdown. Understanding the underlying cause is essential, because treatment strategies differ considerably depending on whether muscle loss is driven primarily by ageing, disease, inactivity, or nutritional deficiency.

How do doctors in the UK diagnose and measure muscle loss?

UK clinicians diagnose muscle loss using EWGSOP2 criteria, combining grip strength, gait speed, and body composition tests such as DEXA; blood tests investigate underlying causes rather than confirming the diagnosis directly.

UK clinicians diagnose loss of muscle mass using a combination of clinical assessment, functional tests, and body composition measurements, guided by the European Working Group on Sarcopenia in Older People (EWGSOP2) criteria (Cruz-Jentoft et al., Age and Ageing, 2019), which are widely referenced in NHS geriatric and frailty services. There is no single definitive test; instead, diagnosis relies on identifying low muscle quantity alongside reduced muscle strength or physical performance.^[1]

Common assessment tools include:

Grip strength measurement using a handheld dynamometer, a simple and validated marker of overall muscle strength
Gait speed testing, where walking speed below a defined threshold suggests functional impairment
The Short Physical Performance Battery (SPPB), which combines balance, gait speed, and chair-stand tests^[1]
Dual-energy X-ray absorptiometry (DEXA or DXA), which provides detailed body composition data including lean muscle mass and is available in specialist NHS centres
Bioelectrical impedance analysis (BIA), a less expensive alternative used in some community and outpatient settings

Diagnostic cut-points for grip strength, gait speed, and muscle mass index vary by population and measurement device; the EWGSOP2 paper and the British Geriatrics Society's Fit for Frailty guidance provide reference values used in UK practice.

Blood tests are used to investigate underlying causes rather than to diagnose muscle loss directly. A GP may request a full blood count, inflammatory markers (CRP and ESR), thyroid function tests, vitamin D levels, HbA1c, vitamin B12 and folate, creatine kinase (where myopathy is suspected), and renal and liver function tests. Low serum albumin can indicate malnutrition contributing to muscle wasting.

Older people identified as frail or pre-frail should receive a comprehensive geriatric assessment that includes evaluation of muscle function, in line with the British Geriatrics Society's Fit for Frailty framework and NHS England frailty resources. Referral to a geriatrician, physiotherapist, or dietitian may follow depending on findings. Early identification is important because muscle loss detected at a mild stage is more responsive to intervention than advanced sarcopenia.

Which treatments and medicines can help rebuild muscle mass?

Resistance exercise combined with adequate protein intake is the most effective treatment; no medicine is licensed in the UK specifically for sarcopenia, though vitamin D, testosterone replacement, and GLP-1 receptor agonists may be used in specific circumstances.

The most effective treatments for loss of muscle mass combine structured resistance exercise with adequate nutritional support, and in some cases, management of an underlying medical condition driving the muscle loss. There is currently no medicine licensed in the UK specifically for sarcopenia, but several pharmacological approaches are used within broader treatment plans.

Nutritional interventions are a cornerstone of management. NICE guidance on nutrition support in adults (CG32) and the British Dietetic Association recommend that adults at risk of muscle loss consume sufficient dietary protein, with older adults often advised to aim for higher intakes than the standard UK reference nutrient intake. Oral nutritional supplements (ONS) prescribed on the NHS, such as high-protein drinks, are used where dietary intake alone is insufficient, in line with NICE CG32 criteria.

Vitamin D supplementation is recommended by the NHS and the Scientific Advisory Committee on Nutrition (SACN) for adults at risk of deficiency, particularly older adults and those with limited sun exposure. Vitamin D supports muscle function and its deficiency is associated with weakness and falls.

Hormone-related treatments are used in specific circumstances. Testosterone replacement therapy may be considered for men with confirmed hypogonadism contributing to muscle loss, following assessment by an endocrinologist. Hormone replacement therapy (HRT) in postmenopausal women may help preserve muscle alongside bone density, though it is not prescribed solely for this purpose.

For people with type 2 diabetes or obesity, medicines such as GLP-1 receptor agonists and the dual GIP and GLP-1 receptor agonist tirzepatide may be used to manage the underlying metabolic condition. In the UK, semaglutide is licensed for chronic weight management as Wegovy and for type 2 diabetes as Ozempic; these are distinct licensed indications and the two brands should not be used interchangeably.^[8]^[9] Tirzepatide is authorised by the MHRA under the brand name Mounjaro for both type 2 diabetes and chronic weight management.^[5]^[6] Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, where tirzepatide or semaglutide may be one option a prescriber considers where clinically appropriate alongside other treatments. Preserving muscle during weight loss requires concurrent resistance training and adequate protein intake, as weight loss alone can reduce lean mass.

What side effects and safety concerns should you know about?

GLP-1 and dual GIP/GLP-1 receptor agonists commonly cause nausea and gastrointestinal upset; serious but rarer risks include acute pancreatitis, gallbladder disease, and hypoglycaemia when combined with insulin or sulfonylureas.

The safety profile of treatments for loss of muscle mass varies considerably depending on the intervention used, and patients should discuss individual risks with their prescriber or pharmacist before starting any new medicine.

GLP-1 and dual GIP/GLP-1 receptor agonists (such as semaglutide and tirzepatide) are associated with gastrointestinal side effects including nausea, vomiting, diarrhoea, and constipation, particularly during dose escalation. These effects are usually transient. The UK SmPC for tirzepatide (Mounjaro) notes that acute pancreatitis has been reported, including post-marketing reports of necrotising pancreatitis and reports with a fatal outcome; patients should be advised to seek prompt medical attention if they develop severe and persistent abdominal pain.^[12]^[13] People with pre-existing pre-proliferative or proliferative diabetic retinopathy should be monitored carefully, as rapid improvement in blood glucose control has been associated with transient worsening of existing diabetic eye disease. Gallbladder disease, including cholelithiasis and cholecystitis, has been reported with this drug class; patients who develop symptoms such as upper abdominal pain, particularly after eating, should seek medical advice. Dehydration resulting from gastrointestinal side effects can increase the risk of acute kidney injury, and patients should be advised to maintain adequate fluid intake. When tirzepatide or semaglutide is used alongside insulin or a sulfonylurea, the risk of hypoglycaemia is increased; dose adjustment of the insulin or sulfonylurea may be required. The UK SmPC's only contraindication for tirzepatide is hypersensitivity to the active substance or excipients.^[12]

For women of childbearing potential, the UK SmPC for tirzepatide (section 4.5) advises using an additional non-oral contraceptive method for four weeks after starting treatment and for four weeks after each dose increase, because delayed gastric emptying caused by tirzepatide may reduce the absorption of oral contraceptives. Tirzepatide and semaglutide should not be used during pregnancy or breastfeeding.

Testosterone therapy carries risks including polycythaemia, cardiovascular effects, and suppression of natural hormone production, and requires regular monitoring as described in the BNF and MHRA Drug Safety Updates.

Corticosteroids, when used long-term for inflammatory conditions, themselves cause muscle wasting and should be used at the lowest effective dose.

Suspected adverse drug reactions can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Can diet and exercise really reverse muscle loss?

Resistance training on at least two days per week, combined with protein spread across meals, can meaningfully slow and partially reverse muscle loss, even in frail older adults, with combined approaches producing the best outcomes.

Diet and exercise can meaningfully slow, halt, and in many cases partially reverse loss of muscle mass, even in older adults, provided the programme is appropriate, consistent, and combined with adequate nutritional support. The evidence base for resistance exercise as the primary intervention for sarcopenia is robust and is reflected in NHS and UK Chief Medical Officers' physical activity guidance.

Resistance (strength) training is the most effective exercise modality for stimulating muscle protein synthesis. Activities such as weight training, resistance band exercises, bodyweight exercises (squats, press-ups), and Pilates all provide mechanical load that signals muscle fibres to grow and strengthen. The UK Chief Medical Officers' Physical Activity Guidelines recommend that older adults engage in muscle-strengthening activities on at least two days per week, and this advice is reflected on NHS exercise guidance pages.^[3]^[4] Even low-intensity resistance exercise has been shown to produce meaningful gains in muscle mass and function in frail older adults when performed consistently.

Protein intake is equally important. Muscle protein synthesis requires an adequate supply of essential amino acids, particularly leucine. British Dietetic Association and ESPEN guidance recommends that older adults at risk of sarcopenia consume protein spread across meals rather than concentrated in one sitting, as this optimises muscle protein synthesis throughout the day. Dairy products, eggs, lean meat, fish, legumes, and soya are all good sources.

Combined approaches produce the best outcomes. A systematic review and meta-analysis (Liao et al., Nutrients, 2022, referenced in NICE evidence reviews) found that combining resistance exercise with protein supplementation produced greater gains in muscle mass and strength than either intervention alone in older adults.

For people losing muscle during weight management, maintaining protein intake and continuing resistance training throughout the weight-loss period is essential to preserve lean mass. Rapid or very low-calorie weight loss without exercise support accelerates muscle loss rather than reversing it.

When should you see a GP about losing muscle mass?

See a GP if you notice progressive unexplained weakness, unintentional weight loss, increasing difficulty with balance, or frequent falls, as these may indicate an underlying condition requiring investigation and specialist referral.

You should see a GP about loss of muscle mass if you notice unexplained or progressive weakness, difficulty with everyday tasks such as climbing stairs or rising from a chair, unintentional weight loss, or frequent falls. These symptoms may indicate an underlying medical condition requiring investigation rather than lifestyle modification alone. A GP can arrange appropriate blood tests, refer to specialist services, and coordinate a multidisciplinary plan.

Contact your GP if you experience:

Noticeable reduction in muscle bulk or strength over weeks to months without an obvious cause
Unintentional weight loss of more than 5 per cent of body weight over six to twelve months, a threshold used in BAPEN's Malnutrition Universal Screening Tool (MUST) and referenced in NICE guidance on nutrition support (CG32)^[2]
Increasing difficulty with balance or mobility
Fatigue disproportionate to your level of activity
Symptoms suggesting an underlying condition, such as excessive thirst, persistent joint pain, or breathlessness

Seek urgent advice via NHS 111 if you develop sudden severe muscle weakness, difficulty swallowing, or breathing difficulties, as these may indicate a neurological or systemic emergency requiring prompt assessment.

Call 999 or go to A&E only if you experience a sudden collapse, loss of consciousness, or signs of a serious acute illness.

For people already taking medicines for weight management or diabetes who notice significant muscle loss, it is important to raise this with the prescribing clinician, as the treatment plan may need to be adjusted to include specific nutritional and exercise support. Older adults identified as frail during a GP review may be referred to a falls prevention service, physiotherapist, or community dietitian under NHS pathways aligned with the British Geriatrics Society's Fit for Frailty framework and NHS England frailty resources. Early intervention consistently produces better outcomes than waiting until muscle loss is advanced.

Scientific References

Frequently Asked Questions

At what age does loss of muscle mass typically begin?

Muscle loss typically begins in a person's thirties and accelerates after the age of sixty, with adults losing an estimated 3 to 8 per cent of muscle mass per decade after middle age, according to the EWGSOP2 sarcopenia consensus.

Can you reverse loss of muscle mass through exercise alone?

Resistance exercise is the most effective single intervention for rebuilding muscle, but combining it with adequate dietary protein produces significantly greater gains in muscle mass and strength than exercise alone, particularly in older adults.

When should loss of muscle mass be investigated by a doctor?

You should see a GP if you experience unexplained progressive weakness, unintentional weight loss, frequent falls, or difficulty with everyday tasks such as climbing stairs, as these symptoms may indicate an underlying medical condition requiring investigation.

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