Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Symptoms of Blood Disorders


David J. Kuter

, MD, DPhil, Harvard Medical School

Last full review/revision Sep 2019| Content last modified Sep 2019
Click here for the Professional Version
Topic Resources

Blood disorders can cause various symptoms in almost any area of the body. Most commonly, symptoms are caused by decreases in the blood components.

Occasionally, symptoms may relate to increases in blood components.

  • Increased red blood cells can cause thickening of the blood (increased blood viscosity) and thereby cause headache and a red complexion (plethora).

  • Increased immune system proteins also can cause thickening of the blood (increased blood viscosity).

  • Increased platelets or blood clotting factors can cause inappropriate excessive blood clotting (thrombosis).

Some blood disorders cause a person's blood to become thickened by increased quantities of immune-related proteins, red blood cells, or platelets. This thickened (more viscous) blood may have difficulty passing through small blood vessels, decreasing blood flow to certain areas of the body, which is a serious condition called hyperviscosity syndrome. Affected people may experience symptoms such as shortness of breath, headaches, dizziness, and confusion. Hyperviscosity syndrome can occur in people who have multiple myeloma, in which it is caused by increased immune system proteins.

Blood disorders often cause symptoms that can also occur in other disorders. For example, the weakness and shortness of breath caused by anemia can be caused by other conditions that impair oxygen delivery to the body, such as heart or lung disorders. On the other hand, easy bruising, a symptom suggestive of a blood disorder, can be caused by conditions other than a blood disorder, especially disorders of the blood vessels or the use of various drugs such as aspirin.

Conditions other than blood disorders can cause bleeding, for example, injuries, surgical procedures, menstrual bleeding or delivery of a baby, and teething in babies. Blood in the urine or stool is usually caused by an abnormality in the urinary or gastrointestinal tract rather than a blood disorder. However, blood disorders can make any bleeding worse. People with blood disorders may experience excessive bleeding following dental procedures or have very heavy menstrual periods.

Some symptoms are more suggestive of a blood disorder. Just a few examples include the following:

  • Blood clot (phlebitis), usually in a leg (most often causing swelling, redness, and/or warmth of the leg or shortness of breath)

  • Petechiae (a fine pin-point red skin rash) caused by too few platelets

  • Blood blisters in the mouth (caused by too few platelets or clotting problems)

  • Swollen lymph nodes caused by white blood cell cancers (such as leukemias or lymphomas)

  • Pallor (pale skin) caused by anemia

  • Pica (eating of ice, dirt, or clay) suggests iron deficiency anemia

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID