I lost 3 kg wight within one month.. without diet and exercise.. I am 24 age....is it dangerous?

Doctor can evaluate. There's always a reason when a person thinks he lost 7 pounds in 1 month. If it is true weight loss, and not caused by an issue with the scales and weighing techniques, then one can work with his doctor to see what vanished: water, fat, muscle, or a combination of them. Whether or not such weight loss is dangerous often depends on the condition of the patient prior to the weight loss.