The causes of drowsiness in three-week-old babies are physiological and pathological, as follows: 1, physiological reasons: consider the recent sleep, such as excessive play before drowsiness, no good rest at night, the next day may be more sleep, you can let the baby sleep at ease, wake up to see the baby’s mental state, if the spirit is normal do not worry; 2, pathological reasons: such as the recent poor feeding, or even nausea, vomiting, diarrhea, etc. Situation, may lead to fatigue, drowsiness, and even cause hypoglycemia, need to go to the hospital in time to improve blood sugar, electrolytes and other related testing, if necessary, to give intravenous rehydration symptomatic treatment. If your baby has a recent history of fever and drowsiness, you should be alert to the combination of central nervous system infection, and need to go to the hospital in a timely manner, as the disease generally affects the child’s spirit and is a little bit heavier, so you need to seek medical attention in a timely manner and do not delay the condition.