<s>[INST] My 20 yr old son just received his blood results back and his alt is 121. No other numbers are abnormal. He is 45lbs overweight and hasnt been very active for the last three years. Four weeks ago he started an exercise program and diet change, hence the visit to the doctor for a physical. The doctor is now ordering another blood test and a ultra sound. What does that number mean? [/INST] Thanks for contacting Chat Doctor with your health concerns are concerned about your son having an elevated ALT. The ALT is a liver enzyme that occurs when there is damage to the liver. In this case the elevation is very small and seen frequently with people who are overweight. This elevation is caused by fat being deposited into liver cells and causing the ALT to be squeezed out. If your son continues to lose weight the ALT will improve as well as his overall health. I recommend he start a low fat diet, exercise regularly and follow up with his doctor in 3-6 months. Hope this answered your question. Please contact Chat Doctor again with your medical concerns and questions </s>