Hello doc i wana increase by weight, my height 6 fut and w' 65kg, can i use injection ? suggest me

Leave it alone: If you are otherwise healthy being skinny is not a disease. As you grow older you will gain weight and look back fondly at these days when you could eat and not get fat. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco or alcohol in any form.

Inject what?: You are mildly underweight which may be a good thing not a bad thing if your weight is stable and you are otherwise healthy. I am not aware of injectable drugs given for the purpose of gaining weight though weight gain may be a side effect of some drugs. If you really want to gain 5-10 lb you should be able to do that with eating more. A hi-calorie bedtime snack on a regular basis could do it.