Why Does Diabetes Cause Excessive Thirst?
We’ve written before about the signs and symptoms of diabetes. While there are a lot of sources about what symptoms diabetes causes, and even some good information about why they’re bad for you, what you don’t often get are the “whys”. And while the “whys” aren’t necessarily critical for your long-term health, they can help you to understand what’s going on with your body and why it acts the way it does. That, in turn, can help with acceptance and understanding of how to better treat the symptoms, which in turn can help you stay on a good diabetes management regimen. In short, you don’t NEED to know why diabetes causes excessive thirst, but knowing the mechanism behind it can make your blood glucose control regimen make more sense and help you stick to it.
So why DOES diabetes cause thirst? First, we’d like to start by saying that excessive thirst is not a good indicator of diabetes. For many people, the symptom creeps up so slowly that it’s almost impossible to determine if your thirst has noticeably increased (unless you keep a spreadsheet of how much water you drink, in which case you also probably get tested pretty regularly anyway). It’s also a common enough symptom that a sudden increase in thirst can mean almost anything. Some conditions that cause thirst increases include allergies, the flu, the common cold, almost anything that causes a fever, and dehydration caused by vomiting or diarrhea. So while excessive thirst is one of those diabetes symptoms that happens, and needs to be addressed, it’s not always a great sign that you should immediately go out and get an A1C test.
Why does diabetes cause thirst?
Excessive thirst, when linked to another condition as a symptom or comorbidity, is called polydipsia. It’s usually one of the earliest symptoms of diabetes to develop, and is often accompanied by excessive dryness of the mouth (“cotton mouth”). In most people with Type 1 or Type 2 diabetes, the thirst builds slowly enough that it is often incredibly difficult to notice until other symptoms present themselves or until the point of major dehydration.
When glucose becomes hyper-concentrated in your bloodstream, usually about 200mg/dL – though this number varies from person to person, your kidney loses the ability to reuptake (pull out) glucose from water. Under normal circumstances, almost all glucose is pulled out of urine and back into the body (as is most of the water, though this depends on how hydrated you are). Since the body can no longer pull glucose out from water in your kidneys, the osmotic pressure (the pressure that builds between a liquid with a high concentration of of solutes and a liquid with a low concentration) builds up. Eventually, it gets so high that water can no longer be absorbed back into your bloodstream, and is in fact being absorbed OUT of your bloodstream.
Side-effects of Type 1 diabetes dehydration
Increased thirst, itself, might seem like a minor problem. The underlying dehydration that causes it, however, is incredibly serious. Immediate effects of not treating severe diabetes-related dehydration can include headaches, nausea, dizziness, and fainting.
For people with diabetes, dehydration can also cause diabetic ketoacidosis. DKA is a condition that causes naturally-occurring acids to build up in the body and can lead to coma, organ failure, or even death.
Even more problematic, severe dehydration actually causes blood sugar levels to rise faster than normal. Part of the reason for this is that the kidneys slowly begin to produce less urine than usual in the presence of prolonged dehydration, and so won’t be able to expel as much excess glucose. A less well-known reason is that dehydration causes the body to release adrenaline and other hormones that act as insulin blockers. For those with Type 2 diabetes, the effect is as if their diabetes had suddenly kicked into overdrive, and glucose stops being broken down almost completely.
If you notice any prolonged symptoms of dehydration, you should immediately schedule an appointment with your physician. If the symptoms include lack of consciousness, shock, or severe impairment, please contact an emergency paramedic team immediately.
Even if you don’t have symptoms of dehydration, drinking plenty of water is an important part of managing a healthy blood glucose level, and staying healthy in general. Bottoms up!