There is no single pill that reliably adds significant weight to an otherwise healthy person. Most medications approved for weight gain are prescribed for specific medical conditions like cancer-related wasting or AIDS, and the over-the-counter options that exist work best when a nutritional deficiency is part of the problem. That said, several prescription drugs, supplements, and appetite stimulants can help tip the scale, depending on your situation.
Prescription Medications for Weight Gain
The pills most likely to produce measurable weight gain are prescription-only, and doctors typically reserve them for people with a medical reason for being underweight. These aren’t lifestyle drugs you can pick up at the pharmacy.
Megestrol acetate is one of the most studied options. Originally a hormonal therapy for certain cancers, it’s also prescribed to stimulate appetite in people with AIDS-related wasting or severe unintentional weight loss. In clinical trials, patients taking the higher dose gained an average of 7.8 pounds over 12 weeks, and 64% gained at least five pounds. The placebo group actually lost weight during the same period. It works, but it carries risks including blood clots, elevated blood sugar, and hormonal disruption, so it’s not something a doctor would prescribe just because you want to bulk up.
Dronabinol is a synthetic cannabinoid approved to treat appetite loss in AIDS patients and nausea from chemotherapy. It increases hunger, but the weight gain tends to be modest compared to megestrol. Side effects can include dizziness, mood changes, and drowsiness.
Oxandrolone is a mild anabolic steroid sometimes prescribed after severe burns, major surgery, or chronic infections where muscle wasting has occurred. It promotes lean tissue gain rather than fat. Because it’s a steroid, it comes with the full list of steroid-related risks (more on that below), though at prescribed doses and short durations the side effects are more manageable than with other anabolic steroids.
Why Anabolic Steroids Are a Bad Shortcut
Some people turn to anabolic steroids without a prescription, hoping for rapid muscle and weight gain. This is genuinely dangerous. In men, steroid misuse can cause shrunken testicles, reduced sperm count, erectile dysfunction, breast development, and an increased risk of testicular cancer. In women, it can trigger excess facial and body hair growth, a deepened voice, menstrual problems, and decreased breast size.
Both sexes face liver and kidney damage, high blood pressure, high cholesterol, severe acne, and significant psychological effects including aggression, mood swings, paranoia, and even hallucinations. Steroids are also addictive. Stopping suddenly can cause withdrawal symptoms. For adolescents, the risks are compounded because steroids accelerate bone aging, potentially stunting growth permanently.
Over-the-Counter Appetite Stimulants
Cyproheptadine is an antihistamine that has a well-known side effect: it makes people hungry. It blocks serotonin and histamine receptors in the brain, which can stimulate appetite. It’s available by prescription in the U.S. but over-the-counter in some countries. Doctors sometimes prescribe it off-label for underweight children or adults who struggle to eat enough. It has mild sedative and anticholinergic effects, meaning it can cause drowsiness and dry mouth, but it’s considered relatively safe compared to hormonal or steroid options.
Cyproheptadine won’t build muscle or change your metabolism. It simply makes you feel hungrier, so you eat more. If your problem is that you can’t consume enough calories, that nudge can be genuinely helpful. If you already eat plenty but don’t gain weight, it’s unlikely to make a difference.
Supplements That May Help
Creatine monohydrate is the most evidence-backed supplement for adding weight quickly. It pulls water into muscle cells, which adds 2 to 4 pounds of fluid weight during the first week or so of use (the “loading phase,” typically 20 grams per day for 5 to 7 days). After that, continued use supports strength and muscle growth during resistance training, which adds real tissue weight over time. Creatine won’t do much if you’re not exercising, but combined with consistent weight training, it’s one of the few supplements that reliably moves the number on the scale.
Protein powders aren’t pills, but protein supplements in capsule or tablet form do exist. They’re far less efficient than shakes or whole food, since you’d need to swallow dozens of capsules to match one scoop of powder. If you’re searching for a pill specifically, protein capsules are an option, but they’re impractical for meaningful calorie intake.
Zinc and vitamin B1 (thiamine) can restore appetite, but only if you’re deficient in them. Zinc deficiency causes appetite loss, changes in taste perception, slow wound healing, and hair loss. Supplementing zinc when you’re low can bring your hunger back to normal. Similarly, vitamin B1 deficiency causes appetite loss along with confusion and other neurological symptoms. If your levels are already normal, taking extra zinc or B1 won’t increase your appetite beyond baseline.
What Actually Drives Weight Gain
Every pill or supplement on this list works through one of two mechanisms: increasing how much you eat, or increasing how much of what you eat gets stored as muscle or fat. None of them override the basic equation. You gain weight when you consistently consume more calories than you burn. For most people who are underweight and otherwise healthy, the real bottleneck is calorie intake, not a missing pill.
If you have a small appetite, eating more calorie-dense foods (nuts, nut butters, olive oil, avocados, whole milk, cheese) can add 300 to 500 extra calories a day without requiring you to eat a much larger volume of food. Eating more frequently, even just adding a fourth or fifth smaller meal, is often more effective than trying to force larger portions at three meals.
If you’ve been trying to gain weight for months without success despite eating more, that’s worth investigating. Conditions like hyperthyroidism, celiac disease, type 1 diabetes, and chronic infections can all prevent weight gain regardless of how much you eat. In those cases, treating the underlying condition matters more than any supplement.
Matching the Right Option to Your Situation
If you’re healthy but naturally thin, creatine plus a calorie surplus and resistance training is the most realistic over-the-counter approach. If you struggle with appetite specifically, cyproheptadine or correcting a zinc or B1 deficiency may help. If you have a medical condition causing weight loss, prescription options like megestrol acetate or dronabinol exist, but these require a diagnosis and a doctor’s involvement because the side effects are real.
There is no safe pill that adds 10 or 20 pounds on its own. The ones that come closest are prescription hormones and steroids with serious trade-offs. For most people searching this question, the answer is less about finding the right pill and more about consistently eating above your calorie needs, ideally while strength training to ensure the weight you gain includes muscle rather than just fat.