Diabetes Mellitus

Consequences of Chronic High Sugars in Other Systems

Jennifer Kong

Learning Objectives

By the end of this section, you will be able to:

  • Explain how manifestations of diabetes mellitus affects other organ systems in the body
  • Identify the consequences of having high blood sugar levels in the body


All types of diabetes mellitus manifest as high blood sugar circulating in the body for a long time. As such, those sugars damage all of the blood vessels in the body – ESPECIALLY the very small microvasculature. Thus, the most common consequences of poorly controlled diabetes are impaired blood flow and thus damage is most common in the eyes, kidneys, and nerves.

  • Nerves:  decreased blood flow will cause loss of nerves responsible for sensation (paresthesia) and movement (e.g. tripping while walking due to foot drop).  As the nerve dies,  tingling and pain develops (diabetic neuropathy).  These problems can manifest in any part of the nervous system – but are more common in the hands, shins, and feet.  Nerves serving the GI system will cause symptoms like gastric paralysis
  • Limbs & digits: blood vessel damage causes poor circulation to limbs and digits.  This can cause tissue death in limbs and digits. As well, hands and feet have a higher risk of injury  which diabetes will complicate wound infection and healing – leading to the possibility of  amputations.
  • Eyes: damage to the retina of the eye will lead to blindness
  • Blood vessels:  Injury & inflammation of the lining of arteries can lead to  atherosclerosis and ischemic heart disease, heart attacks and strokes (see Atherosclerosis chapter for more background)
  • Kidneys:  damage to microvasculature will lead to a  loss of filtering ability in the kidneys leading to renal disease and eventual renal failure

DHPLC Specimen PATH 425-053 – Diabetic glomerulosclerosis – kidney stained with Periodic acid -Schiff stain. Created by Jennifer Kong licensed under All rights reserved

 At the same time, high blood sugar is present in both the blood and bodily fluids (e.g. urine, saliva). This creates a very favourable environment for metabolic disturbances, bacterial growth and hence infections.
  • urinary & oral infections:  there are many  pathogens in the genitourinary & oral cavities. Thus high sugar in urine/saliva will encourage growth
  • open wounds:  high blood sugar can promote bacterial growth in the wound, thus delaying healing.  As well, diabetes causes poor blood flow thus leading to slow or poor wound healing
  • Liver disease (non-alcoholic fatty liver disease): the constantly high blood sugar wreaks havoc on nutrient processing and storage in the liver. the liver is the storage site for starch (glycogen) in response to insulin; it also converts nutrients like sugars into fats where it is stored in liver.  As  a result, diabetes can lead to liver disease as excessive storage of these nutrients are harmful to the liver cells.

Critical thinking Exercises


Section Summary

Diabetes involves chronic hyperglycemia  will cause tissues to change their shape and function – particularly the walls of small blood vessels.  As a result, less blood can flow in this vasculature resulting in less blood being delivered to tissues.  Thus, chronic hyperglycemia affects all tissues but is most noticeable in the kidneys (i.e. poor blood filtration causing retention of wastes and loss of nutrients into urine). nervous (i.e. lack of sensation), eyes (i.e. partial or full blindness), and fingers/toes (i.e. can lead to starving or dying tissue).  As glucose metabolism is disturbed, fat metabolism is dominant causing high circulating levels of fat which will also affect blood vessels (i.e. atherosclerosis leading to heart disease and strokes) and liver (i.e. liver damage due to storage of fat created by impaired glucose metabolism).

Review Questions


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Pathology Copyright © 2022 by Jennifer Kong is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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