Blood tests

This fish is suffering from massive haematemesis which, one the one hand, is very bad news, but on the other hand, makes it very easy to do a blood test.

There are a lot of blood tests. Like, billions. We are going to tell you about the key ones.

Full Blood Count (FBC)

This is common to do. It's pretty much your standard. Especially important to do in infection, heart problems, surgery and anaemia.

• White blood cell (WBC) tells you about of white blood cells per volume of blood. Normal is around 4-11x10⁹/L. Low means immunosuppression, high means infection or cancer.

White blood cell differential looks at the types of white blood cells present:

• • Neutrophils (40-75%) (raised in bacterial infection)
  • Lymphocytes (20-45%) (raised in viral or bacterial infection, and in haematological cancer)
  • Monocytes
  • Eosinophils
  • Basophils
• Haemoglobin is the amount of Hb in the blood. Normal is around 13-18g/dL in men and 11.5-16g/dL in women. High means dehydration, cancer or lung disease. Low is anaemia: check the page for causes.
• Platelet count is the number of platelets. Normal is around 150-400x10⁹/L. Low points to cancer, chemo or autoimmune problems, whilst high signifies haematological cancer.
• Mean corpuscular volume (MCV) is average size of your red cells. Its raised in some anaemia, and lowered in others. Visit the Causes of anaemia page for more on types.

Clotting (CLS)

There are a variety of tests they do, such a Prothrombin Time (PT) and Partial Thromboplastin Time (PTT). Basically though, they are used to test people before surgery, to test the effectiveness of anticoagulation or to isolate weird bleeding disorders, such as Haemophilia and von Willibrand's disease.

Urea and Electrolytes (U+Es)

Generally used to assess the workings of the kidney, and to check that electrolytes are in balance, and the patient isn't gonna drop dead.

• Sodium (Na⁺)
  • low is hyponatraemia: from sodium loss (d&v, excessive sweating, kidney disease or Addison's), from excess fluids (drinking too much water, heart failure, cirrhosis, nephrotic syndrome). Sometimes your body makes too much ADH, leading to extra water and thus low sodium.
  • high is hypernatraemia: almost always due to dehydration. Rarely, due to increased salt intake, Cushing's syndrome, or diabetes insipidus.
• Potassium (K⁺) -
• Creatinine -
• Urea -
• Calcium (Ca²⁺)-
• Albumin -
• Proteins -