Sunken fontanel is a sign of dehydration.

• A. True
• B. False
• C. Sometimes
• D. Not applicable

Answer: (A)

In infants, the status of the fontanelle is a useful clue about hydration. A sunken fontanelle occurs when body fluids are reduced, making the soft spot on the top of the head appear depressed relative to the skull. The more sunken it is, the more likely dehydration is, especially when you see other signs such as dry mucous membranes, lack of tears, decreased urine output, and lethargy. Keep in mind that this sign is most relevant in young children with open fontanelles and may not be present in every dehydrated infant, but its presence strongly supports dehydration and helps gauge severity when combined with other findings.