At 21, being tall and weighing 50 kg suggests you are underweight. There are no magic medicines for weight gain that have zero side effects. The safest, most effective way to build muscle is through a nutrient-dense, calorie-surplus diet combined with consistent strength training. For safe, well-researched supplements, you can use generic whey protein to help meet your daily protein targets and creatine monohydrate to support muscle strength. Avoid unregulated weight-gain pills, which can carry health risks. I highly recommend speaking with a doctor or registered dietitian first to rule out any underlying metabolic conditions and to safely guide your progress.

Being underweight can happen due to fast metabolism, low appetite, poor dietary intake, stress, digestive issues, or sometimes underlying health problems like thyroid imbalance or nutrient deficiencies. The goal of healthy weight gain is not just eating more, but eating balanced, nutrient-rich food that helps build muscle and strength instead of only fat. Try increasing your meal frequency by having small, calorie-dense meals every 2-3 hours, and include foods like rice, chapati, potatoes, nuts, peanut butter, dairy products, eggs, lentils, and healthy oils in your diet. Adding protein is important because it helps in muscle growth and improves body strength. Light strength exercises or resistance training can also help convert extra calories into healthy muscle rather than fat. Proper sleep and stress control are equally important because poor rest can affect appetite and metabolism. If weight is not improving despite a good diet or if there are symptoms like fatigue, diarrhoea, or appetite loss, it is important to get a medical check-up to rule out underlying causes.