15 Terrible Diseases You Could Have Without Even Knowing

We’ve all been there; your throat feels scratchy and your temperature is high. It may be easy to spot the flu, but not every disease is easy to detect. The following conditions could be wreaking havoc on your body, and you don’t even know it. One type of cancer feels like gas and cramps, so it often goes undetected for years (page 10).

1. Deep vein thrombosis

Man sitting and stretching

Sitting all day can raise your risk of developing deep vein thrombosis. | iStock.com

  • Symptoms: redness, pain, swelling, warmth, and tenderness in the affected area

According to MedlinePlus, deep vein thrombosis is a blood clot that forms in a vein, often in the lower leg or thigh. If the clot breaks loose and travels to your lungs, this can cause low blood oxygen levels, serious lung damage, or death. The National Heart, Lung, and Blood Institute says only about half of those with DVT experience symptoms. A doctor can test you for blood clots, but it’s important to regularly move to lower your risk, too.

Next: You don’t want issues with this kind of sugar.

2. Diabetes

Man checking his blood sugar levels

You can have diabetes and not even know. | iStock.com

  • Symptoms: feeling thirsty, tired, or hungry

You can be born with type 1 diabetes, but developing type 2 can happen as you age. The American Diabetes Association explains the condition causes blood glucose levels to rise because your body fails to use the hormone insulin, which helps regulate blood sugar. Unfortunately, people feel hungry, thirsty, or tired for many reasons, so it’s difficult to detect type 2 diabetes early on.

Next: The second leading cause of blindness in the U.S.

3. Glaucoma

Close up of a woman's eye

Glaucoma affects the eyes and can cause blindness. | iStock.com/Jean-Philippe Wallet

  • Symptom: pressure behind the eyes

Unfortunately, glaucoma is the second leading cause of blindness in the U.S., and it comes with few to no symptoms, John Berdahl, M.D., writes for All About Vision. All eye disorders associated with glaucoma damage the optic nerve, which carries information from the eye to the brain. When the disease advances, you can experience peripheral vision loss or total blindness.

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4. Celiac disease

Man holding his head while laying down

Celiac disease often comes with no symptoms. | iStock.com

  • Symptoms: fatigue, joint pain, depression, migraines, and iron or vitamin deficiency

Although tons of people profess to be gluten-free, many people with celiac disease still don’t know they have it. This autoimmune disorder damages the small intestine when you eat gluten, a protein found in rye, wheat, or barley, according to the Celiac Disease Foundation. While it may seem like you’d notice if gluten doesn’t agree with you, more than 200 symptoms exist, and no two cases look alike.

Next: Things literally break down for older adults.

5. Osteoporosis

Man holding his knee in pain

This disease literally means “porous bones.” | iStock.com

  • Symptoms: No clear signs or symptoms exist.

Those with osteoporosis have weak bones due to bone density loss. The National Osteoporosis Foundation says the disease is responsible for over 2 million broken bones per year. Some people lose height if it affects their vertebrae. Still, it can take years for those with osteoporosis to notice, and many people only realize it after a fracture. Make sure to get enough calcium and vitamin D.

Next: Doctors can overlook this mental illness for years.

6. Bipolar disease

Man and wife arguing with hand on hip

This mental illness can masquerade as many issues in adulthood. | IT Stock Free/iStock/Getty Images

  • Symptoms: intensely elevated moods and feelings of grandiosity

Doctors often misdiagnose bipolar disease as attention deficit-hyperactivity disorder in children. Also known as manic-depressive illness, it may not be identified until adulthood. University of Pittsburgh Professor of Psychiatry, Dr. David A. Axelson, told CBS, “The best tip-off is that mania of bipolar illness is episodic, whereas the behavior is chronic in ADHD.” If you’re concerned, consult a mental health professional.

Next: The body will start attacking itself.

7. Lupus

Doctor and patient

Be your own health advocate. | Gpointstudio/iStock/Getty Images

  • Symptoms: joint pain, sores, bruising, fatigue, and rashes that look like scars

Often overlooked by doctors, this degenerative autoimmune disorder tricks the body into thinking brain and organ tissue are hostile and attacking it, according to Prevention. Sadly, lupus is incurable and tends to appear between the teen years and mid-40s.

Next: Is your personal waste management system out of whack?

8. Chronic kidney disease

doctor writing on a medical chart.

Doctors often miss this chronic illness. | Bojan89/iStock/Getty Images

  • Symptoms: headaches, loss of appetite, itchy skin, muscle cramps, swelling or numbness of the hands and feet

We can thank our kidneys for keeping our bodies chemically balanced. But when the kidneys are permanently damaged, aka chronic kidney disease, waste gathers in the bloodstream. Of the 10 to 20 million people with CKD, “7.4 million have less than half the filtering capacity of a healthy young adult,” according to WebMD. The majority of this group don’t know they have CKD. If left untreated, it can lead to kidney failure, heart attack, or stroke.

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9. Sleep apnea

Portrait of a man sleeping soundly in his bedroom.

Sleeping man | Minerva Studio/iStock/Getty Images

  • Symptoms: heavy snoring, fatigue, tiredness, and poor concentration

About 90% of people with sleep apnea aren’t diagnosed. Doctors don’t learn a lot about the condition in medical school, according to CBS News, so they can overlook it. Denying it may seem fine, but sleep apnea is linked to increased chances of heart attack and stroke.

Next: This type of cancer masquerades as gas and cramps.

10. Colon cancer

Man holding stomach as he struggles with constipation

Colon cancer often has no signs or symptoms. | iStock.com

  • Symptoms: gas, cramps, diarrhea, fatigue, constipation, weight loss

Colon cancer may be the sneakiest of all. According to Mayo Clinic, this cancer starts in the large intestine as small polyps that grow to become cancer. Past the beginning stages, it causes consistent diarrhea or constipation. Though colon cancer is one of the most treatable cancers in its early stages, many people skip their screenings and don’t discover it until it’s too late.

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11. Huntington’s disease

Doctor holding a tablet to give diagnosis

Huntington’s disease is incurable. | iStock.com

  • Symptoms: amnesia, mental confusion, muscle spasms, difficulty speaking

A rare but fatal disease, Huntington’s breaks down your brain’s nerves, explains the Huntington’s Disease Society of America. You can have the genetic disorder through adolescence without knowing it. The symptoms are described as a cross between ALS, Parkinson’s, and Alzheimer’s due to the way your body and brain are compromised. You may start noticing symptoms between the ages of 30 and 50, but it’s tough to detect.

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12. Oral cancer

girl with a serious sore throat

Lesions can trigger other symptoms. | patrisyu/iStock/Getty Images

  • Symptoms: changes in speech, swelling issues, or a consistently sore throat

Your doctor may misdiagnose tongue or tonsil cancer if you don’t have a history of smoking. However, according to CBS News, “One in five of these cancers is attributable not to tobacco use but to infection with human papillomavirus (HPV).” Once it spreads to the lymph nodes, a doctor may catch it; before then it may only appear as lesions in the back of the throat.

Next: You may not think it’s possible to contract this disease.

13. Hepatitis C

Woman talking to doctor about her symptoms

Hepatitis C can cause a range of problems with the liver. | iStock.com

  • Symptoms: abdominal pain, yellow eyes, gastrointestinal bleeding, nausea, fatigue

A virus that attacks your liver, the World Health Organizations says hepatitis C is often spread through injection equipment for drug usage, but it can also occur through sexual contact. While some have an acute infection that clears itself within six months, it can become chronic and lead to liver damage.

There’s about a two-week window from when you contract the disease to when symptoms show. However, roughly 80% of cases don’t exhibit symptoms. In order to minimize your risk, limit sexual partners and practice good hygiene.

Next: Get tested no matter your age or lifestyle.

14. Chlamydia

Woman upset about her diagnosis

Chlamydia is one of the most common STDs in the U.S. | iStock.com

  • Symptoms: genital pain, abnormal discharge, vaginal bleeding

Many people who have chlamydia don’t know due to its lack of symptoms. The infection can damage a woman’s fallopian tubes, which can lead to infertility or an increased risk of an ectopic pregnancy, says MedicineNet. Chlamydia can live in the cervix, urethra, vagina, rectum, or throat, and it can pass from mother to child during birth. If you’re sexually active, you should get tested in case you have this (or any) STD.

Next: Make sure you pass the test for this disease.

15. Gonorrhea

Couple sleeping in bed

Gonorrhea is a very common STD. | iStock.com

  • Symptoms: burning during urination, penis discharge, swollen testicles; vaginal bleeding between periods and painful urination

According to the Centers for Disease Control and Prevention, gonorrhea is another common STD without symptoms. And symptoms, especially in women, can be mistaken for a bladder infection. As with all STDs, condoms greatly reduce your risk. It’s important to get tested regularly if you’re sexually active.