To safely gain weight and overcome weakness, we must first rule out underlying issues like anaemia or vitamin deficiencies. Focus on a calorie-surplus diet rich in lean proteins, healthy fats, and complex carbohydrates rather than relying solely on pills. For supplements, a high-quality whey protein can help meet your protein targets, and a daily multivitamin can address nutritional gaps causing weakness. Creatine is also effective for building strength when paired with resistance training. Please avoid unregulated weight-gain pills, as they can contain harmful ingredients. I highly recommend consulting a doctor for basic blood tests before starting any supplement regimen.