There is no fixed duration for giving Himalaya Mentat syrup, and it should be used only on a doctor’s advice. If your 4-year-old son has delayed or unclear speech, he should be assessed by a paediatrician and a speech therapist to identify the underlying cause. Himalaya Mentat syrup is a herbal supplement used to support cognitive health, but there is no strong medical evidence that it improves speech development. Medicines alone are usually not enough, and early speech therapy and interactive learning are more effective. Please avoid long-term use of any syrup without medical review.