Iron is a very important mineral found in every cell of the body, which is why lacking it can cause both small and lasting health problems.

The essential nutrient is needed to make the oxygen-carrying proteins hemoglobin, found in red blood cells, and myoglobin, found in muscles, according to the National Institutes of Health (NIH).

Lack of iron is the most common known form of nutritional deficiency. Its prevalence is highest among young children and women of childbearing age and pregnant women, the Centers for Disease Control and Prevention (CDC) says.

The recommended daily dietary allowance for iron for 19-to-50-year-old women is 18 milligrams and 8 mg for men. It doesn’t sound like much, but between 10 and 15 percent of adults in the U.S. don’t have enough and thousands are hospitalized every year.

Losing 100 hairs a day is normal but if you’re seeing a lot more than that every time you brush your hair, this may be a sign you lack iron. Iron deficiency can lead to anemia. When that happens, the hair follicles don’t get enough oxygen, which the body uses just for vital functions because it’s in survival mode, and the hair falls out. Treatment for hair loss is enhanced when iron deficiency, with or without anemia, is treated, according to a review of several studies.

Fatigue is one of the most common symptoms of iron deficiency. People are used to being in a hurry all the time so many don’t pay attention when their body feels tired. However, if you don’t have enough iron, there is less oxygen going to your muscles, which then have no energy, leaving you feeling exhausted and weak. Hemoglobin is a protein that helps red blood cells deliver oxygen throughout your body.

Poor skin tone is common when the body lacks iron. The skin, being the largest organ on the body, will inevitably suffer if there are not enough red blood cells to deliver oxygen to it. Paleness is generally the result of reduced blood flow or a decreased number of red blood cells (anemia).

Naturally, if the oxygen level in your body is low, you’ll feel out of breath much quicker than normal. If you feel like you can’t catch your breath after going up one flight of stairs, you may need to have some iron-rich foods such as liver, beans, nuts, dried fruits, green vegetables, according to the U.K. National Health Service (NHS).

Headache, especially with activity, can be a sign of iron deficiency. Unfortunately, a headache is also a symptom people often ignore even though it can sometimes be life-threatening. Your body’s priority when it doesn’t have enough oxygen is to get it to the brain before other organs. But even then the arteries can swell, triggering headaches, according to American Society of Hematology.

Your body absorbs more iron from meat than it does from other sources, according to the Mayo Clinic. So if you stay away from meat, you have to find another way to increase your intake of iron-rich, plant-based foods. Many people opt out for supplements. If meat is out of the question for you, pick foods that are high in Vitamin C to enhance iron absorption. Such foods include broccoli, melons, kiwi, leafy greens, peppers, tomatoes, oranges.

If you don't have enough hemoglobin-carrying red blood cells, your heart has to work harder to move oxygen-rich blood through your body, according to the National Heart, Lung and Blood Institute.

Less oxygen, caused by lack of iron, wakes up the sympathetic nervous system, which activates what is often termed the fight or flight response, according to ScienceDaily. When you add heart palpitations to this symptom, you feel anxious and restless. Also, lack of oxygen, including to the brain, as a result of anemia will slow cognition.

The nail has raised ridges and is thin and curved inward. This disorder is associated with iron deficiency anemia, according to NIH. The fingernails consist of hardened layers of protein, which protects the soft tissue. When the body is not making enough hemoglobin, the lack of oxygen weakens the nail, causing them to break.

Iron is required by most organisms as an essential cofactor in many important biological processes; the immune system is depending on it. So, naturally, if you don’t have enough of it, you are more susceptible to illnesses. The spleen is part of your lymphatic system, which fights infection, according to NIH. If the spleen is not getting enough oxygen because of iron deficiency, it can’t work as well. The lymph nodes, which produce white blood cells to fight infections, don’t get enough oxygen either, causing weaker white blood cells.

Unexplained cold hands and feet are a common symptom if iron deficiency, according to Iron Disorders Institute. Consuming less than 18 mg for women and 8 mg for men prevents the production of myoglobin and hemoglobin. They can’t deliver oxygen to red blood cells and tissues, inducing the hands and feet.

Less iron means less myoglobin in the blood which keeps the muscles healthy. Since the tongue is actually a muscle, it will feel sore, smooth, swollen and will have a weird pale color, according to John Hopkins Medicine. Sore and swollen tongue can, as a result, leads to problems with chewing, swallowing and even speaking.

Loss of appetite and weight loss is another general symptom of anemia, according to NHS. It usually is a result of other symptoms people are experiencing. When you have a headache, you feel weak (because your muscles don’t have enough oxygen due to lower red blood cells count), and you are sick, you don’t usually feel hungry, do you?

A condition, called Pica, which is a craving for non-nutritive things like ice, hair, paper, stones, dirt or glass, is another symptom. It doesn’t happen very often and there is not a clear explanation as to why the disorder develops, but it has been known to happen, according to case studies.

RLS is condition in which people feel an irresistible urge to move the legs. About 15 percent of people who have RLS also have iron deficiency, according to John Hopkins Medicine. The single most consistent finding and the strongest environmental risk factor associated with RLS is iron insufficiency. The symptoms usually occur at night, preventing patients from getting enough sleep.