While most people can tell when they are coming down with a cold, there are many other conditions that are far harder to detect or identify. Some of them are quite serious and require a doctor’s attention. Consider the following examples.

Vitamin malabsorption or malabsorption syndrome is a condition in which the body doesn’t absorb nutrients from food properly. It has many causes that can include parasitic infestations or bacterial or viral infections that damage the intestinal wall and prevent nutrients from reaching their destinations. 

Other causes include celiac disease, lactose intolerance, and cystic fibrosis. Symptoms of malabsorption syndrome can include flatulence, bloating, frequent diarrhea, scaly skin rashes, and weight loss. Vitamin malabsorption can also cause abnormalities in the stool, such as bad odor, bulkiness, or unusually pale color.

Doctors will use a variety of tests to both diagnose vitamin absorption and identify the cause. For example, they could take a stool sample and look for abnormalities like too much fat. They may also use an endoscopy or biopsy to examine the patient’s intestines. Treatment will depend on the cause of the malabsorption.

Sleep apnea is a common and serious disorder in which the patient momentarily and repeatedly stops breathing while asleep. Symptoms of sleep apnea include snoring, restlessness during sleep, suddenly waking up to a choking or gasping sensation, waking up with a dry mouth or sore throat, feeling tired or sleepy during the day, and difficulty waking up in the morning. Anybody sharing a bed with the patient is likely to notice some of the symptoms before they do.

Sleep apnea doctors will question the patient and members of their household about their sleep patterns. They may decide to conduct a sleep study at the patient’s house or in a lab. Treatment will depend on the severity and cause of the sleep apnea.

Celiac disease is an autoimmune disorder in which the immune system attacks the small intestine after the patient has ingested gluten, a protein often found in grains. The small intestine is eventually damaged and thus unable to absorb nutrients properly.

Many of the symptoms are those seen in any digestive tract disorder: nausea, diarrhea, abdominal pain, and so on. Other symptoms can include anemia, sores around the mouth, itchy skin rash, joint pain, and neurological problems.

A doctor will perform blood tests to look for antibodies in the patient’s blood. They might also perform an endoscopy, and they might take a skin biopsy if the patient has a rash. Currently, the only treatment for celiac disease is a gluten-free diet. 

Hashimoto’s disease, also known as chronic lymphocytic thyroiditis, is an autoimmune disorder affecting the thyroid. It is the most common cause of hypothyroidism in the United States. The symptoms are generally those typical of hypothyroidism and can include increased sensitivity to cold, a puffy face, dry and pale skin, unexplained weight gain, constipation, lack of energy, hair loss, and brittle nails.

The doctor will perform blood tests to check the patient’s thyroid hormone levels and to look for antibodies. Synthetic thyroid hormones are the most common treatment.

All of the described conditions are chronic conditions that can eventually cause serious complications like heart problems. Anybody who has experienced symptoms of these disorders that last more than a couple of weeks should see their doctor.