The earliest signs of anemia from low iron are usually ongoing fatigue, weakness, and skin that looks paler than usual, often showing up before a routine blood test would flag anything unusual. Other early clues include shortness of breath during normal activity, a fast or pounding heartbeat, and cold hands or feet. Iron deficiency has several possible causes, most of them manageable but a few that need prompt medical attention.

1. Inadequate Dietary Iron Intake

What it is: Not getting enough iron from food to keep up with the body's needs for making red blood cells.

Why it happens: Diets low in iron-rich foods such as red meat, poultry, seafood, beans, and fortified cereals, or diets that rely mostly on plant sources without enough vitamin C to help absorption, can leave iron stores gradually depleted.

Common symptoms: Slowly building fatigue, weakness, pale skin or pale inner eyelids, feeling cold more often than usual, and mild shortness of breath with exercise.

Risk factors: Vegetarian or vegan diets without careful planning, picky eating in young children, and older adults eating smaller or less varied meals.

When to seek evaluation: If fatigue or paleness lasts more than a couple of weeks despite eating reasonably well, ask a doctor for a simple blood test.

2. Heavy Menstrual Periods

What it is: Iron deficiency caused by losing more blood, and therefore more iron, during monthly periods than the diet can replace.

Why it happens: Conditions such as uterine fibroids, adenomyosis, or hormonal imbalances can cause periods that are heavier or longer than typical, steadily draining iron stores over months.

Common symptoms: Fatigue that is worse around or right after your period, pale skin, dizziness when standing up quickly, and needing to change menstrual products very frequently or passing large clots.

Risk factors: Fibroids, certain IUDs, bleeding disorders, and perimenopause.

When to seek evaluation: Periods that soak through a pad or tampon every hour for several hours in a row, or that last longer than seven days, should be evaluated.

3. Pregnancy

What it is: Iron deficiency that develops because pregnancy increases the body's need for iron to support the growing baby and a larger blood volume.

Why it happens: The body needs noticeably more iron during pregnancy than before it, and diet or existing iron stores may not keep pace with that demand.

Common symptoms: Tiredness beyond typical pregnancy fatigue, pale skin, dizziness, a rapid heartbeat, and cravings for non-food items such as ice or dirt, a sign known as pica.

Risk factors: Closely spaced pregnancies, carrying twins or multiples, and entering pregnancy with low iron stores.

When to seek evaluation: Iron levels are checked routinely at prenatal visits; report unusual fatigue or pica cravings to your OB provider between visits.

4. Gastrointestinal Bleeding from Ulcers or Gastritis

What it is: Slow, ongoing blood loss from irritation or a sore in the stomach or upper intestine that depletes iron over time.

Why it happens: Long-term use of NSAID pain relievers, an H. pylori infection, or excess stomach acid can wear away the stomach lining and cause small amounts of bleeding that may not be obvious day to day.

Common symptoms: Fatigue and paleness along with stomach discomfort, dark or tarry-looking stools, or nausea after eating.

Risk factors: Regular NSAID use, H. pylori infection, heavy alcohol use, and a history of ulcers.

When to seek evaluation: Dark, tarry, or black stools, or persistent stomach pain, need prompt medical evaluation.

5. Reduced Iron Absorption

What it is: Iron deficiency that develops even with adequate dietary intake because the intestine cannot absorb iron normally.

Why it happens: Conditions such as celiac disease, inflammatory bowel disease, or previous gastric bypass or other stomach surgery can limit how much iron the intestine takes in.

Common symptoms: Fatigue and pallor along with digestive symptoms such as bloating, diarrhea, or unexplained weight loss, depending on the underlying condition.

Risk factors: Diagnosed celiac disease, Crohn's disease, prior weight-loss surgery, and long-term use of acid-reducing medications.

When to seek evaluation: Anemia that does not improve with iron supplements deserves further testing for an absorption problem.

6. Anemia of Chronic Disease or Inflammation

What it is: A type of anemia that develops alongside a long-term illness, even when iron stores are not severely low.

Why it happens: Ongoing inflammation from conditions such as rheumatoid arthritis, chronic kidney disease, or a long-term infection can interfere with how the body uses stored iron to make red blood cells.

Common symptoms: Fatigue, weakness, and pale skin that tend to develop slowly alongside the symptoms of the underlying condition.

Risk factors: Chronic kidney disease, autoimmune conditions, cancer, and long-term infections.

When to seek evaluation: If you have a known chronic condition and notice new or worsening fatigue, mention it at your next appointment.

7. Colorectal or Other Gastrointestinal Cancer

What it is: A less common but serious cause of iron deficiency anemia, where a growth in the digestive tract causes slow, often unnoticed blood loss.

Why it happens: A tumor in the colon or elsewhere in the digestive tract can bleed gradually over weeks or months, steadily draining the body's iron stores without obvious symptoms at first.

Common symptoms: Fatigue and pallor along with a change in bowel habits, unintended weight loss, or blood in the stool that may be visible or hidden.

Risk factors: Age over 45 to 50, a family history of colorectal cancer, and inflammatory bowel disease.

When to seek evaluation: New iron deficiency anemia in a man or a postmenopausal woman without an obvious cause should prompt a doctor to look for a source of internal bleeding, which may include a colonoscopy.

When to Seek Medical Care