Blood in the stool is one symptom that shouldn't be explained on its own. Yes, it could be caused by hemorrhoids or an anal fissure, but when combined with diarrhea, mucus, pain, frequent urination, or weakness, your doctor should think outside the box.<\/p>\n
In such a situation, laboratory diagnostics usually begin with an assessment of the consequences of blood loss. A complete blood count helps to see the level of hemoglobin, red blood cells, hematocrit, white blood cells, and platelets. If blood loss continues for a long time, anemia may develop. If there is active inflammation, white blood cells or platelets may change.<\/p>\n
The next important area is iron stores. Ferritin, iron, transferrin, and transferrin saturation help to understand whether the body's reserves are depleted due to chronic blood loss or inflammation. This is especially important if the patient complains of weakness, palpitations, dizziness, pallor, rapid fatigue, or shortness of breath with normal exertion.<\/p>\n
Blood in the stool does not confirm ulcerative colitis by itself. But it changes the priority of the examination: it is necessary not only to relieve the symptom, but also to determine the source of the bleeding.<\/p>\n
Scenario two when diarrhea lasts for weeks<\/strong><\/h2>\nIf diarrhea persists for several days after an apparent food mistake, a doctor is more likely to suspect an acute infection or food reaction. But if the diarrhea is frequent, recurs for weeks, occurs at night, is accompanied by mucus, pain, or weight loss, an inflammatory nature of the symptoms should be investigated.<\/p>\n
Faecal calprotectin is of particular importance in this scenario. It is a protein marker in the stool that reflects the presence of inflammation in the gut. NICE recommends faecal calprotectin as a test that can help doctors distinguish inflammatory bowel disease from irritable bowel syndrome in adults with new lower gastrointestinal symptoms when referral to a specialist is being considered and cancer is not suspected.<\/p>\n
Elevated calprotectin does not equal a diagnosis of ulcerative colitis. It can also be elevated in Crohn's disease, intestinal infections, and other inflammatory conditions. But this analysis helps distinguish a situation where organic inflammation is likely from a situation where symptoms are more like a functional disorder.<\/p>\n
You can read more about the interpretation of this indicator in the article about calprotectin in feces<\/a>, which explains why the result should be evaluated together with symptoms, and not as a standalone diagnosis.<\/p>\nScenario three when symptoms resemble an intestinal infection<\/strong><\/h2>\nUlcerative colitis and intestinal infections can present with similar symptoms: diarrhea, abdominal pain, fever, mucus or blood in the stool. Therefore, infectious causes must be ruled out before a definitive diagnosis can be made, especially if symptoms are acute in onset.<\/p>\n
Stool tests may include tests for bacterial pathogens, parasitic infections, viral causes if indicated, and Clostridioides difficile, especially if symptoms were preceded by antibiotics or hospitalization. The Mayo Clinic notes that stool tests help rule out other disorders, including infections, and the presence of white blood cells or certain proteins in the stool may indicate ulcerative colitis.<\/p>\n
This step is important for a practical reason: the treatment of infectious colitis and ulcerative colitis can be significantly different. If you mistakenly attribute an infection to chronic inflammation or vice versa, you can lose time and worsen the condition.<\/p>\n
Scenario four when there is weakness, anemia, and weight loss<\/strong><\/h2>\nSometimes a patient presents with weakness rather than diarrhea as the primary complaint. Laboratory tests may show low hemoglobin, low ferritin, elevated inflammatory markers, or signs of nutrient deficiencies. In such a situation, intestinal symptoms should be asked about separately, as people do not always immediately associate weakness with bowel movements.<\/p>\n
The Crohn's and Colitis Foundation notes that the diagnosis of ulcerative colitis is based on medical history, physical examination, and medical tests; blood tests may show signs of infection or anemia, which may indicate bleeding in the colon or rectum.<\/p>\n
In this scenario, the doctor may assess:<\/p>\n
\n- complete blood count;<\/li>\n
- ferritin;<\/li>\n
- iron;<\/li>\n
- transferrin;<\/li>\n
- saturation transferrin<\/a>;<\/li>\n
- C-reactive protein;<\/li>\n
- ESR;<\/li>\n
- albumin<\/a>;<\/li>\n
- total protein;<\/li>\n
- electrolytes<\/a>;<\/li>\n
- creatinine;<\/li>\n
- liver indicators;<\/li>\n
- vitamin B12 and folic acid as indicated.<\/li>\n<\/ul>\n
These tests not only bring you closer to a diagnosis, they show how much the disease has already affected the body.<\/p>\n
Scenario five: when you need to distinguish ulcerative colitis from Crohn's disease<\/strong><\/h2>\nUlcerative colitis and Crohn's disease belong to the same group of conditions, inflammatory bowel diseases. But they are different conditions. Ulcerative colitis affects the colon and rectum, while Crohn's disease can affect different parts of the digestive tract.<\/p>\n
Lab tests can show inflammation, anemia, or deficiencies, but they don't always accurately distinguish one disease from another. The Crohn's and Colitis Foundation explains that endoscopy and colonoscopy play an important role in making a diagnosis, distinguishing between Crohn's disease and ulcerative colitis, assessing disease activity, and monitoring complications.<\/p>\n
That is why, when inflammatory bowel disease is suspected, the doctor may combine blood tests, stool tests, endoscopy with biopsy, and, if necessary, imaging methods. In the material about Crohn's disease<\/a> It explains in more detail why a single test cannot replace a complete diagnostic pathway.<\/p>\n![\"Stool](\"https:\/\/medilab.km.ua\/wp-content\/uploads\/2026\/09\/analizy-kalu-pry-vyrazkovomu-koliti.jpg\")
<\/p>\n
Laboratory minimum which often becomes the starting point<\/strong><\/h2>\nThere is no single test for ulcerative colitis. The initial set depends on symptoms, age, duration of complaints, presence of blood, temperature, anemia, and concomitant conditions.<\/p>\n
Most often, the doctor starts with several directions.<\/p>\n
Scenario three when symptoms resemble an intestinal infection<\/strong><\/h2>\nUlcerative colitis and intestinal infections can present with similar symptoms: diarrhea, abdominal pain, fever, mucus or blood in the stool. Therefore, infectious causes must be ruled out before a definitive diagnosis can be made, especially if symptoms are acute in onset.<\/p>\n
Stool tests may include tests for bacterial pathogens, parasitic infections, viral causes if indicated, and Clostridioides difficile, especially if symptoms were preceded by antibiotics or hospitalization. The Mayo Clinic notes that stool tests help rule out other disorders, including infections, and the presence of white blood cells or certain proteins in the stool may indicate ulcerative colitis.<\/p>\n
This step is important for a practical reason: the treatment of infectious colitis and ulcerative colitis can be significantly different. If you mistakenly attribute an infection to chronic inflammation or vice versa, you can lose time and worsen the condition.<\/p>\n
Scenario four when there is weakness, anemia, and weight loss<\/strong><\/h2>\nSometimes a patient presents with weakness rather than diarrhea as the primary complaint. Laboratory tests may show low hemoglobin, low ferritin, elevated inflammatory markers, or signs of nutrient deficiencies. In such a situation, intestinal symptoms should be asked about separately, as people do not always immediately associate weakness with bowel movements.<\/p>\n
The Crohn's and Colitis Foundation notes that the diagnosis of ulcerative colitis is based on medical history, physical examination, and medical tests; blood tests may show signs of infection or anemia, which may indicate bleeding in the colon or rectum.<\/p>\n
In this scenario, the doctor may assess:<\/p>\n
\n- complete blood count;<\/li>\n
- ferritin;<\/li>\n
- iron;<\/li>\n
- transferrin;<\/li>\n
- saturation transferrin<\/a>;<\/li>\n
- C-reactive protein;<\/li>\n
- ESR;<\/li>\n
- albumin<\/a>;<\/li>\n
- total protein;<\/li>\n
- electrolytes<\/a>;<\/li>\n
- creatinine;<\/li>\n
- liver indicators;<\/li>\n
- vitamin B12 and folic acid as indicated.<\/li>\n<\/ul>\n
These tests not only bring you closer to a diagnosis, they show how much the disease has already affected the body.<\/p>\n
Scenario five: when you need to distinguish ulcerative colitis from Crohn's disease<\/strong><\/h2>\nUlcerative colitis and Crohn's disease belong to the same group of conditions, inflammatory bowel diseases. But they are different conditions. Ulcerative colitis affects the colon and rectum, while Crohn's disease can affect different parts of the digestive tract.<\/p>\n
Lab tests can show inflammation, anemia, or deficiencies, but they don't always accurately distinguish one disease from another. The Crohn's and Colitis Foundation explains that endoscopy and colonoscopy play an important role in making a diagnosis, distinguishing between Crohn's disease and ulcerative colitis, assessing disease activity, and monitoring complications.<\/p>\n
That is why, when inflammatory bowel disease is suspected, the doctor may combine blood tests, stool tests, endoscopy with biopsy, and, if necessary, imaging methods. In the material about Crohn's disease<\/a> It explains in more detail why a single test cannot replace a complete diagnostic pathway.<\/p>\n<\/p>\n
Laboratory minimum which often becomes the starting point<\/strong><\/h2>\nThere is no single test for ulcerative colitis. The initial set depends on symptoms, age, duration of complaints, presence of blood, temperature, anemia, and concomitant conditions.<\/p>\n
Most often, the doctor starts with several directions.<\/p>\n
Sometimes a patient presents with weakness rather than diarrhea as the primary complaint. Laboratory tests may show low hemoglobin, low ferritin, elevated inflammatory markers, or signs of nutrient deficiencies. In such a situation, intestinal symptoms should be asked about separately, as people do not always immediately associate weakness with bowel movements.<\/p>\n
The Crohn's and Colitis Foundation notes that the diagnosis of ulcerative colitis is based on medical history, physical examination, and medical tests; blood tests may show signs of infection or anemia, which may indicate bleeding in the colon or rectum.<\/p>\n
In this scenario, the doctor may assess:<\/p>\n
- \n
- complete blood count;<\/li>\n
- ferritin;<\/li>\n
- iron;<\/li>\n
- transferrin;<\/li>\n
- saturation transferrin<\/a>;<\/li>\n
- C-reactive protein;<\/li>\n
- ESR;<\/li>\n
- albumin<\/a>;<\/li>\n
- total protein;<\/li>\n
- electrolytes<\/a>;<\/li>\n
- creatinine;<\/li>\n
- liver indicators;<\/li>\n
- vitamin B12 and folic acid as indicated.<\/li>\n<\/ul>\n
These tests not only bring you closer to a diagnosis, they show how much the disease has already affected the body.<\/p>\n
Scenario five: when you need to distinguish ulcerative colitis from Crohn's disease<\/strong><\/h2>\n
Ulcerative colitis and Crohn's disease belong to the same group of conditions, inflammatory bowel diseases. But they are different conditions. Ulcerative colitis affects the colon and rectum, while Crohn's disease can affect different parts of the digestive tract.<\/p>\n
Lab tests can show inflammation, anemia, or deficiencies, but they don't always accurately distinguish one disease from another. The Crohn's and Colitis Foundation explains that endoscopy and colonoscopy play an important role in making a diagnosis, distinguishing between Crohn's disease and ulcerative colitis, assessing disease activity, and monitoring complications.<\/p>\n
That is why, when inflammatory bowel disease is suspected, the doctor may combine blood tests, stool tests, endoscopy with biopsy, and, if necessary, imaging methods. In the material about Crohn's disease<\/a> It explains in more detail why a single test cannot replace a complete diagnostic pathway.<\/p>\n
<\/p>\nLaboratory minimum which often becomes the starting point<\/strong><\/h2>\n
There is no single test for ulcerative colitis. The initial set depends on symptoms, age, duration of complaints, presence of blood, temperature, anemia, and concomitant conditions.<\/p>\n
Most often, the doctor starts with several directions.<\/p>\n