Excessive Thirst: Why You May Always Feel Thirsty and When to Be Checked

What it involves

MedlinePlus describes excessive thirst, also called polydipsia, as an abnormal feeling of always needing to drink fluids. It says thirst is often just the body's reaction to fluid loss during exercise or to salty food, but it can also point to a condition that needs treatment.

Who this is for

• Patients who feel constantly thirsty and are drinking much more than they used to
• Patients with thirst that comes with blurry vision, tiredness or heavy urination
• Patients taking a water pill or another medicine who noticed the thirst afterward
• Patients with a family history of diabetes who want their blood sugar checked

What to expect

• Questions about when the thirst began, how it changes through the day and whether urination has changed
• A review of your diet, activity, medicines and any recent illness or injury
• Blood and urine tests, which MedlinePlus lists for this symptom, including a glucose level
• A plan that follows the cause, such as diabetes care if blood sugar is high

When thirst is just thirst

Thirst is the body's signal to replace lost water, and MedlinePlus says it is most often appropriate to drink until the feeling goes away. A salty or spicy meal, a sweaty workout or a day in the heat all explain it. Drinking plenty of water is healthy in most cases. The question for a provider is whether the thirst matches what you have been doing. Thirst that returns minutes after you drink, wakes you at night or does not match your activity is the pattern worth describing.

High blood sugar is the one to rule out

The encyclopedia notes that excessive thirst may be a symptom of high blood sugar, which may be due to diabetes that is not controlled. Thirst often travels with passing more urine and feeling tired, and the frequent urination guide describes that side of the same pattern. A simple blood glucose level is the first test MedlinePlus lists, and the prediabetes and A1C guide explains the longer-term number. Finding high blood sugar early is much easier to manage than finding it years later.

Other causes on the list

MedlinePlus names several other causes. Diabetes insipidus, a different condition from diabetes mellitus, can cause heavy thirst and urination. Some medicines can do it, including anticholinergics, demeclocycline, diuretics and phenothiazines. Large fluid losses from the bloodstream into the tissues, as in severe infections, burns, or heart, liver or kidney failure, can also produce thirst, and so can bleeding enough to lower blood volume. Psychogenic polydipsia, a mental disorder involving a very strong, constant urge to drink, is on the list too.

What the visit looks like

The provider takes a history and does a physical exam. According to MedlinePlus, questions cover how long you have been aware of the thirst, whether it came on suddenly or slowly, whether it stays the same all day, and whether you changed your diet, activity or weight. They also ask about urine output, bleeding, sweating, swelling, fever and any recent burn or injury. Tests that may be ordered include blood glucose, a complete blood count, calcium, sodium, serum osmolality, a urinalysis and urine osmolality. The urinalysis guide explains one of them.

Signs to act on

MedlinePlus says to contact your provider if the thirst is ongoing and unexplained, if it comes with other unexplained symptoms such as blurry vision or fatigue, or if you are passing more than 5 quarts of urine a day, which is about 4.75 liters. If the thirst follows vomiting or diarrhea, dehydration may be the cause, which the stomach flu and dehydration guide covers. Confusion, fainting or a very fast heartbeat with thirst needs urgent care, not an appointment next week.

Treating the cause rather than the thirst

The encyclopedia is plain that the provider recommends treatment based on the exam and test results, and gives an example: if tests show diabetes, you will need to be treated for it. For thirst caused by diabetes, it says to follow the prescribed treatment to keep blood sugar controlled. The practice offers diabetes management visits as part of primary care. If a medicine is behind the thirst, ask your provider about it instead of cutting back on your own.

Sources

• MedlinePlus — Thirst, excessive