Does HMB Help Recovery After Surgery? What the Studies Show

HMB is often promoted as a way to support surgery recovery, especially by helping people maintain muscle and strength while they heal. Surgery can increase muscle breakdown at the same time that pain, poor appetite, fasting, and inactivity make it harder to eat enough calories and protein and stay active. This can be especially important for older adults, frail patients, and people who are already at risk of muscle loss. However, the research on HMB after surgery is more complicated than the marketing often suggests. Some studies report benefits, while others find little or no benefit. Many studies also combined HMB with other nutrients or exercise, making it difficult to know how well HMB works by itself.

What Is HMB?

HMB stands for beta-hydroxy-beta-methylbutyrate. Your body makes a small amount of it when it metabolizes leucine, an essential amino acid found in protein.

HMB appears to stimulate muscle protein production and reduce muscle protein breakdown. This is why researchers have studied it in older adults, people confined to bed, cancer patients and others at risk of losing muscle.

That rationale makes sense after surgery. An operation increases physical stress while pain, fasting, poor appetite and inactivity can reduce calorie and protein intake. But a plausible mechanism does not prove that a supplement improves recovery.

Does HMB Improve Recovery After Surgery? What 11 Studies Found

In 2025, researchers combined the results of 11 controlled studies involving 575 surgical patients to see what the evidence showed overall. This type of research is called a meta-analysis. The operations included hip-fracture repair, cardiac surgery, cancer surgery, liver transplantation and endoscopic procedures.

Five studies used HMB as a stand-alone supplement. Six combined it with arginine and glutamine. Four also incorporated exercise. The trials generally provided 3 grams of HMB per day, although the individual trial reports and formulations were not identical.

Compared with people who did not receive HMB, those who used HMB-containing supplements:

• Spent about one less day in the hospital
• Had fewer reported complications
• Walked farther during a six-minute walking test
• Showed improvement in some measures of arm and limb muscle

HMB-containing supplements may help some people walk better, experience fewer reported complications, or leave the hospital sooner after surgery. However, HMB did not clearly improve overall lean body mass, body weight, BMI, or blood albumin levels.

Some of these results sound encouraging, but they need some context. The studies included different types of surgery and did not all define complications in the same way. The researchers judged the evidence for shorter hospital stays and fewer complications as moderate, while the evidence for several other benefits was weaker. They also noted possible study bias and publication bias.

What Do These Studies Really Show?

The results suggest that HMB-containing supplements may help some surgical patients, but they do not prove that HMB alone works. The studies used different surgeries, formulas, treatment periods, and definitions of complications, making it difficult to identify who benefits most.

What Happened When People Took HMB Before Heart Surgery?

In a 2022 study, 70 people scheduled for heart surgery were assigned to take either a supplement or a placebo.

For 30 days before surgery, the supplement group took:

• 3 grams of HMB
• 14 grams of L-arginine
• 14 grams of L-glutamine

People who took the supplement spent less time in the hospital and intensive care unit:

• Hospital stay: 5 days compared with 6 days
• ICU stay: 2.5 days compared with 3.5 days

The supplement group also had lower blood markers linked to heart muscle damage and a better score for overall organ function after surgery.

These results are encouraging, but the study did not test HMB by itself. Because the supplement also contained large amounts of arginine and glutamine, we cannot tell how much of the benefit came from HMB.

Did HMB Help Older Adults Recover After Heart Surgery?

A 2025 study followed 44 adults aged 65 or older who were preparing for heart surgery. Their average age was about 72.

For at least two weeks before surgery, one group took a supplement containing HMB, arginine, and glutamine. Some people took one serving per day, while others took two, depending on their kidney function.

After surgery, the supplement group performed better on a six-minute walking test:

• Supplement group: 428.9 meters
• Control group: 304.5 meters

They also had better grip strength, leg strength, walking speed, and overall physical performance.

The average hospital stay was:

• 16.1 days with the supplement
• 20.4 days without it

However, the supplement did not produce a clear improvement in muscle mass. The researchers also reported no serious kidney or liver problems related to the supplement.

Important Limitation

The researchers planned to enroll 200 people but enrolled only 44. The study was also open-label, meaning participants and researchers knew who received the supplement. These limitations make the improvements in walking and hospital stay less certain.

Did HMB Help People Recover After Abdominal Cancer Surgery?

Not every surgery study found a benefit.

In this trial, 60 people having open surgery for abdominal cancer took either a placebo or a supplement containing HMB, arginine, and glutamine. They started it three days before surgery and continued for seven days afterward.

The main question was whether the supplement reduced wound problems after surgery.

The results showed:

• Wound complications occurred in 20% of both groups
• No clear difference in other complications
• No clear difference in hospital stay
• No improvement in muscle mass
• No improvement in handgrip strength

The researchers concluded that the supplement did not reduce wound complications after open abdominal cancer surgery.

This study is important because it shows that HMB-containing supplements do not always improve recovery. Based on current research, HMB should not be promoted as a proven way to improve wound healing after surgery.

Does HMB Help Recovery After Liver Surgery?

A recent study attracted attention for suggesting that HMB might help after liver surgery. However, the study was done in mice, not people.

The mice received HMB for 10 days before surgery, but they stopped taking it when the operation took place.

Seven days later, the mice given HMB had lower blood levels of ALT and AST, two signs of liver cell damage. Researchers also found changes suggesting that HMB helped the mitochondria, the parts of cells that produce energy, keep working during liver recovery.

The researchers also gave some mice a toxic dose of acetaminophen after the liver had regrown. Mice that had taken HMB before surgery showed better energy-producing activity in their liver cells after this second injury. That result is interesting, but it does not reflect normal recovery after surgery.

This study suggests that HMB before liver surgery may reduce some signs of liver damage and help liver cells produce energy in mice. It does not prove that HMB helps people recover faster, prevents complications, or shortens the hospital stay after liver surgery. Human studies are still needed.

Does HMB After Surgery Help Prevent Muscle Loss?

The results are mixed.

Some studies found that people taking HMB-containing supplements had better arm or limb muscle measurements, greater strength, or better walking ability. Other studies found no clear improvement in total muscle mass or lean body mass.

This means HMB may help some people function better even when it does not produce a noticeable increase in muscle size.

That could still be useful during recovery, especially for standing, walking, and taking part in physical therapy. However, larger studies are needed before we know how reliable this benefit is.

How Much HMB Did the Studies Use?

Most studies used about 3 grams of HMB per day, often split into two 1.5-gram servings.

However, that does not mean 3 grams is the right dose for every person or every type of surgery. Some studies started HMB several weeks before surgery. Others began only a few days beforehand and continued after the operation.

Researchers still do not know:

• The best time to start taking HMB
• How long to continue it after surgery
• Whether it works better before or after surgery
• Whether HMB alone works as well as formulas that also contain arginine, glutamine, or protein
• Which surgical patients are most likely to benefit

Is It Safe to Take HMB Before Surgery?

Do not start HMB or any other supplement before surgery without checking with your surgeon.

Some HMB-containing supplements may contain other ingredients such as arginine, glutamine, vitamin D, calcium, protein, herbs, or sweeteners. Those ingredients may not be suitable for everyone.

Talk with your doctor before using HMB if you have a serious medical condition, take prescription drugs, have trouble swallowing, follow a medically prescribed diet, or have been told to stop supplements before surgery.

Does HMB Have Side Effects?

HMB has generally been well tolerated in human studies, and serious side effects do not appear to be common. Some people may experience stomach discomfort, nausea, diarrhea, or constipation.

Many HMB supplements also contain protein, arginine, glutamine, calcium, vitamin D, herbs, sweeteners, or other ingredients. These added ingredients may cause side effects or may not fit a person’s medical diet or treatment plan.

What About HMB and Cancer?

HMB can activate a muscle-building pathway called mTOR, much like the amino acid leucine. In muscle, this is a normal process that helps the body make new protein and repair tissue.

Some cancers also use the mTOR pathway to grow. However, this does not mean that HMB has been shown to feed cancer or make tumors grow faster. Activating mTOR for a short time in muscle is not the same as the abnormal, constantly active mTOR signaling found in some cancer cells.

HMB has been studied in people with cancer-related muscle loss, and researchers have not clearly linked it to faster tumor growth. One problem, though, is that only a small amount of research has directly measured what happens to tumors, so long-term cancer safety remains uncertain.

Anyone with active cancer should ask their oncologist before taking HMB, especially if they are receiving a drug that targets the mTOR pathway.

How Do You Choose an HMB Supplement?

Choose a product that clearly lists how much HMB it provides in each serving. Avoid proprietary blends that hide the amount.

Because supplement quality can vary, look for independent testing from organizations such as NSF, USP, or ConsumerLab.

Check the label carefully because HMB products may contain:

• HMB by itself
• HMB with vitamin D
• HMB with protein
• HMB with arginine and glutamine

These products are not the same. Many surgery studies tested HMB as part of a combination formula, so the results may not apply to HMB taken by itself.

My Opinion: Is HMB Worth Considering After Surgery?

HMB looks more promising for surgical recovery than I expected. However, if it really helps, I suspect the greatest benefits would occur in people who are malnourished, bedridden, frail, or already have poor strength and physical function. It should still be viewed as one part of a recovery plan that includes enough protein, enough calories, and rehabilitation.

Bottom Line: Does HMB Help After Surgery?

HMB may help some people walk better, have fewer complications, or leave the hospital sooner after surgery. However, the evidence is not strong enough to recommend it for everyone.

The biggest unanswered question is whether 3 grams of HMB by itself improves recovery or whether the benefits come from combining HMB with other nutrients, enough protein, and rehabilitation.

For now, the research looks promising, but it does not provide a clear answer.

Good nutrition and physical rehabilitation matter more than HMB. A supplement cannot make up for too little food or protein, an untreated nutrient deficiency, or not following the recovery plan your medical team gives you.

Have you used HMB before or after surgery?