[mital]

How can I will increase my weight in to 10 to 15 days ?

[Curlyben]

Simple eat more empty calories.
There is NO "medicine" to accomplish this.

[joypulv]

There is no medicine for increasing weight, nor can it be done safely in 2 weeks or even more.
How old are you? Do you eat a pretty healthy diet? Is all your family thin, and how do they feel about this with you?

[UhnonimuS]

In the course of 2 weeks, if you wish to gain weight, you will have to change your current eating habits.
If you don't eat breakfast, start eating breakfast, and if you eat breakfast, make sure you eat a lunch and dinner too.
I would also recommend having a second dinner. Say you usually eat dinner at 5 o clock, well by 7:30, you're body may not say,
"I'm hungry." but it definitely won't say, "I'm full" either. Your last meal (second dinner) can be eating whatever you want, just make sure,
You eat until you are completely full. The food stored over night while you are sleeping, will provide a nice chunk of weight gain,
When seen over the course of two weeks. Try to actually refrain from physical activity. We're not trying to burn calories, we're trying to gain them.

Hope this helps.