Megestrol is classified as a high-risk medication primarily because it increases mortality in elderly patients, suppresses the adrenal glands, and promotes fat gain rather than healthy weight. Despite being widely prescribed as an appetite stimulant, particularly in nursing homes, the evidence shows it often causes more harm than benefit, especially in older adults. It appears on the Beers Criteria, a list maintained by the American Geriatrics Society of medications that are potentially inappropriate for people 65 and older.
Higher Death Rates in Nursing Home Residents
The most alarming risk is the association with increased mortality. A large retrospective study matched 709 nursing home residents taking megestrol with 1,418 similar residents who were not. The median survival for those on megestrol was 23.9 months, compared to 31.2 months for those who never took it. That is roughly seven fewer months of life. Making matters worse, the megestrol group did not even gain significantly more weight than the untreated group. So the drug shortened survival without delivering the benefit it was prescribed for.
Of the 709 residents who received megestrol, 39.4% died in the nursing home during the study period, compared to 32.4% of those who did not receive the drug. These were elderly patients with an average age of about 84, a population already vulnerable to medication side effects.
Adrenal Suppression Can Be Life-Threatening
Megestrol acts as a partial mimic of cortisol, the body’s primary stress hormone. When you take it regularly, your adrenal glands slow down their own cortisol production because the drug is partially doing the job for them. This is called adrenal suppression, and it creates a dangerous situation: if you stop the medication abruptly, get sick, have surgery, or face any physical stress, your body may not be able to produce enough cortisol to respond.
Symptoms of adrenal insufficiency include low blood pressure, nausea, vomiting, dizziness, and weakness. The FDA labeling warns explicitly that failure to recognize this suppression “may result in death.” This risk applies both while taking the drug and during the withdrawal period after stopping it. Patients coming off megestrol may need supplemental stress-dose steroids during illness or surgery, sometimes for weeks after their last dose.
Weight Gain Is Mostly Fat, Not Muscle
Megestrol is typically prescribed to stimulate appetite in people losing weight from cancer, AIDS, or age-related frailty. It does increase appetite in many cases. The problem is what kind of weight comes back. Studies consistently show that megestrol increases body fat while decreasing body protein. In animal research, the proportion of weight gained as fat was 47.3% with megestrol alone, and the drug actively inhibited the accumulation of lean mass.
This distinction matters enormously for frail or chronically ill patients. What they need is muscle and functional tissue. What megestrol gives them is adipose tissue, which does not improve strength, mobility, or the ability to recover from illness. The drug also lowers testosterone levels, which further works against muscle preservation. For an elderly person in a nursing home, gaining fat while losing protein is arguably worse than maintaining a stable lower weight.
Blood Clot Risk
As a synthetic progestational agent, megestrol carries a theoretical risk of venous thromboembolism, including deep vein thrombosis and pulmonary embolism. The clinical data on this is mixed. One early retrospective report from a nursing home found that 6 out of 18 patients on megestrol developed deep vein thrombosis, though two of those patients had independent risk factors (endometrial cancer and a recent fracture). Most cases appeared after 50 or more days of treatment.
Larger randomized studies have not replicated those numbers. One prospective trial with 72 patients on megestrol and 73 on placebo reported zero cases of deep vein thrombosis in either group. The risk likely exists but may be lower than initially feared, and it is concentrated in patients who already have clotting risk factors such as immobility, cancer, or recent surgery.
Why It Persists Despite the Risks
Megestrol remains in use largely because clinicians feel pressure to “do something” about weight loss in frail patients, and there are few pharmaceutical alternatives with strong evidence. The American Academy of Family Physicians recommends against using prescription appetite stimulants in older adults altogether. Their guidance favors non-drug approaches: optimizing social support during meals, discontinuing other medications that suppress appetite, providing appealing food, offering feeding assistance, and clarifying the patient’s own goals.
Systematic reviews of other appetite-stimulating drugs, including cannabinoids, anabolic steroids, and thalidomide, have not found adequate evidence for their safety or effectiveness in promoting weight gain either. Mirtazapine, an antidepressant, commonly causes weight gain as a side effect, but there is little evidence supporting its use purely as an appetite stimulant in patients who are not depressed. In short, the alternatives are limited, which is partly why megestrol continues to be prescribed despite its risk profile.
Who Faces the Greatest Risk
The risks of megestrol are highest in people over 65, particularly those living in long-term care facilities. This population tends to have reduced kidney function, lower physiological reserves, and a higher baseline risk of blood clots, falls, and infections. Adrenal suppression is especially dangerous in this group because even a partial loss of cortisol response can become a crisis during a common event like a urinary tract infection or a bout of pneumonia.
The FDA labeling notes that elderly patients are more likely to have decreased kidney function and recommends monitoring renal function during treatment. Any patient on chronic megestrol therapy who develops low blood pressure, unexplained nausea, dizziness, or unusual weakness should be evaluated for adrenal insufficiency promptly, whether they are currently taking the drug or have recently stopped it.