According to the Mayo Clinic, the signs and symptoms may depend on age. For adults, signs such as diarrhea, fatigue, weight loss, bloating and gas, abdominal pain, constipation, vomiting, and nausea are common. However, there are also other symptoms that are not related to the digestive system. These are anemia, osteoporosis or osteomalacia, itchy skin, damaged teeth enamel, mouth ulcers, numbness in the feet and hands, hyposplenism, and heartburn.
As for children under 2 years old, the symptoms are vomiting, chronic diarrhea, swollen belly, failed growth, poor appetite, and muscle wasting. On the other hand, older children have the symptoms of diarrhea, constipation, weight loss, irritability, delayed puberty, ADHD, and even learning disabilities.
If anyone notices these symptoms, then it is best to consult a doctor as soon as possible.