Clenbuterol will cause your body temperature to rise a half degree or so. This is because your body is burning more energy from fat. You won’t feel uncomfortable with the temperature change. This is not a drug for long term use as the effectiveness of it will diminish over time. The length of time it will be effective depends on the individual but it is likely to be from 4-6 weeks. A sign that it is no longer working is that your body temperature returns to normal. Increasing the dose won’t help. You can try to stop using it for a few weeks and then try it again.