When can diarrhea cause dehydration in a baby?

What does the evidence show for baby diarrhea and dehydration?

• Look for a change from the baby’s normal stool pattern, not simply the loose texture common with some milk feeds. Diarrhea can have infectious, dietary or other causes. Blood, marked abdominal swelling or severe pain requires a closer assessment. 1
• Reduced urination, a dry mouth, fewer tears and a sunken soft spot can accompany dehydration. Marked sleepiness, sunken eyes or cool discolored extremities is more concerning. Contact the pediatrician when signs appear rather than waiting for a numerical diaper threshold. 2
• Breastfeeding can usually continue during diarrhea. A commercial oral electrolyte solution may be advised when extra replacement is needed, but the amount depends on the baby and the illness. Severe dehydration may require hospital fluids rather than a home drinking plan. 3
• Juice, soda and sports drinks have unsuitable sugar and salt concentrations for replacing diarrheal losses. Do not mix a homemade electrolyte recipe. Over-the-counter antidiarrheal medicines are not recommended for children under two and should not be given to an infant without medical direction. 1
• A fever changes urgency in a young infant: under three months, a rectal temperature of 100.4°F or higher warrants immediate medical advice. Do not assume diarrhea or a recent food change makes that fever routine. 4

When should I call my provider about baby diarrhea and dehydration?

Call the pediatric team promptly for fewer wet diapers, dry mouth, unusual sleepiness, inability to keep feeds down or refusal to drink. Bloody stool, green vomit, severe belly pain or swelling needs urgent assessment. Call 911 if the baby is limp, unresponsive, struggling to breathe or collapsing. Fever at or above 100.4°F rectally in a baby under three months needs immediate medical advice.