© Getty Images

Celiac disease -

Celiac disease is an immune reaction to gluten that triggers inflammation in the small intestine. People with celiac have digestive problems when eating gluten-containing foods, and about half suffer with diarrhea and weight loss.

© Shutterstock

Celiac disease -

It takes the average patient about six to 10 years to get a proper diagnose. This is because many also suffer with symptoms that are present in other diseases, such as itchy skin, headaches, joint pain, and heartburn. However, a blood test can help diagnose it.  

© Shutterstock

Polycystic ovary syndrome -

Symptoms of polycystic ovary syndrome (PCOS) include irregular periods, unexplained weight gain, and difficulty getting pregnant. PCOS, a hormonal disorder, affects women of reproductive age.

© Shutterstock

Polycystic ovary syndrome -

A common symptom of this condition are enlarged ovaries with numerous small cysts, but not everyone with enlarged ovaries has PCOS.  To be diagnosed, women need to also have infrequent or prolonged periods or elevated levels of male hormones, called androgens. 

© Shutterstock

Multiple sclerosis -

Multiple sclerosis (MS) is another autoimmune disease that attacks the body's nerve cells and damages the communication between the brain and the rest of the body. 

© Shutterstock

Multiple sclerosis -

Early signs of MS can be episodic and might include numbness, weakness, or tingling in one or more limbs. Once a doctor suspect MS, a spinal tap or MRI can confirm the diagnosis.

© Shutterstock

Diabetes -

Before signs of diabetes develop, adults can have it for years without knowing it. Leaving it untreated can cause life-threatening damage to the body's major organs.

© Shutterstock

Diabetes -

To avoid developing any severe problems, watch out for earlier symptoms like increased thirst, hunger, frequent urination, sudden weight loss, and fatigue.

© Shutterstock

Cluster headaches -

Cluster headaches are rare, but extremely painful. They tend to occur close together on the same day, and last on average 30 minutes to three hours. 

© Shutterstock

Cluster headaches -

It's still not known why cluster headaches exist, but they tend to occur when seasons change. For this reason, they're often misdiagnosed as allergy-related sinus headaches.

© Shutterstock

Rheumatoid arthritis -

Rheumatoid arthritis (RA) is an autoimmune disorder that causes unexplained aches and pains. It can occur at any age, and often includes inflammation and painful swelling of joints.

© Shutterstock

Rheumatoid arthritis -

Early stages of RA can mimic many other conditions, which makes it hard to diagnose. A diagnosis usually starts with a blood test that can detect any inflammation in the body. Then, a doctor needs to take into account the patient's medical history and do a careful physical analysis before settling for RA. 

© Shutterstock

Fibromyalgia -

Fibromyalgia is a widespread musculoskeletal pain that doctors often describe as having medically unexplained symptoms.

© Shutterstock

Fibromyalgia -

Doctors often diagnose for fibromyalgia when they can't find a root cause for a patient's chronic pain and fatigue. It involves them having to rule out other diseases, some that are equally difficult to diagnose. 

© Shutterstock

Hypothyroidism -

Also known as underactive thyroid, hypothyroidism is a condition in which the thyroid gland produces an insufficient amount of the hormones that help regulate weight, energy, and mood. 

© Shutterstock

Hypothyroidism -

The early stages of the condition are subtle and can mimic depression, fibromyalgia, and many other conditions, which is why it's often misdiagnosed. 

© Shutterstock

Inflammatory bowel disease -

There are primarily two types of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. Both cause inflammation of the digestive tract, including pain and diarrhea.

© Shutterstock

Inflammatory bowel disease -

Because there's no test for IBD, a diagnosis of elimination is required until it's narrowed down to this condition. It involves many tests, such as imaging, blood tests, and assessments.

© Shutterstock

Endometriosis -

As most healthy women deal with menstrual pain and discomfort, endometriosis is often misdiagnosed. The condition causes the uterine tissue to grow outside the uterus. 

© Shutterstock

Endometriosis -

Women with endometriosis often report pelvic pain, cramping, and heavy bleeding that gets worse over time. An ultrasound or laparoscopy is required for a definite diagnosis.

© Shutterstock

Lupus -

One of the most distinctive signs of lupus is a butterfly-shaped rash across a patient's cheeks, but that's not the case for everyone. Lupus can also affect the joints, kidneys, brain, skin, and the lungs. 

© Shutterstock

Lupus -

The diagnosis for this chronic inflammatory disease can be a long and difficult process, as the symptoms are similar to other diseases. Doctors will ask for blood and urine tests, along with a complete physical exam, to reach a diagnosis. 

© Shutterstock

Irritable bowel syndrome -

Irritable bowel syndrome (IBS) is a chronic condition that affects the large intestine. It causes abdominal pain, cramping, bloating, diarrhea, and/or constipation. 

© Shutterstock

Irritable bowel syndrome -

There's no test to prove the condition, so doctors require a diagnosis of elimination. A patient need to have symptoms for at least six months before a formal evaluation. 

© Shutterstock

Migraines -

Migraines are usually characterized by severe headaches that cause an intense throbbing or pulsing. It's often accompanied by nausea, vomiting, or sensitivity to light and sound.

© Shutterstock

Migraines -

Some may not even know that they're suffering from migraine, others can suffer from severe symptoms that cause paralysis.

© Shutterstock

Appendicitis -

An inflamed or burst appendix isn't actually easy to identify. Typical symptoms include nausea, pain, and tenderness around the belly button. 

© Shutterstock

Appendicitis -

For people who have an appendix that points backward instead of forward in the body, symptoms can appear in a different location. 

© Shutterstock

Lyme disease - A sign of Lyme disease is a bullseye rash that can form around the tick bite. However, not everyone develops this rash, which can get confusing as other symptoms include fatigue, headaches, joint pain, and flu-like symptoms.

© Shutterstock

Lyme disease -

If you've been bitten by a tick, make sure to remove it immediately to prevent the transfer of dangerous bacteria. If you suffer from any signs or symptoms, a blood test can show if there are any antibodies for Lyme disease.

Sources: (Health) (Healthline)

See also: Understanding dysautonomia: the invisible illness affecting millions 

© Shutterstock