Why is my old cat drinking so much water?

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During the summer it’s common for cats, particularly senior cats, to be sensitive to the heat, and therefore drink a bit more water than usual. It’s hot, so your cats will consume more water to cool themselves down, pretty normal behavior. If you’re noticing your old cat has been drinking much more water all of a sudden, this can be a concerning problem. Excessive thirst (also known as polydipsia), and as a result excess urination, is a symptom of a number of serious health issues in cats. This is not a sign you should just brush off and wait to see if it gets better. However, this doesn’t mean your cat is on the verge of death. Most of these medical issues are easily treatable and your cat can live many healthy years with proper treatment.

How much water are cats supposed to drink?

In order to figure out how much water is too much water, you should probably first know how much water is enough in the first place. While all cats are different, cats generally need between 3.5–4.5 ounces of water per 5 pounds of body weight every day. If your cat eats dry food, they’ll probably drink (or at least should drink) more water than a cat that eats only wet food. If your cat eats mostly wet food you’ll probably notice they’ll drink less out of their water dish, since they’re getting their water from food as well as from what they drink.

So how do you know how much water your cat is drinking?

First method is to simply use a liquid measuring cup to fill their water dish up with a specific amount of water. See how long it takes them to finish that amount, and you’ll be able to roughly figure out how much they drink every day.

The most accurate way, however, is to get a water dish with measurements on it, like this adorable one. Keep notes on the day/time you fill the bowl up, and how much is left at the end of each day. Then you’ll be able to see if your cat is drinking more water than the average cat, or if the amount they’re drinking is increasing. If your cat seems to be drinking a lot of water, you’ll want to make an appointment with your vet.

Your senior cat's drinking habits can be due to a number of physical and psychological reasons.

Why is my cat drinking a lot of water?

Excessive thirst is a symptom of numerous medical conditions in cats, both physical and mental. While it’s often the first obvious symptom of a problem, it’s usually accompanied by other symptoms. Read the lists of symptoms here carefully, as it might help you decide what’s wrong with your cat.

Stress or Anxiety

If you’ve been to senior-cats.com before, you probably have noticed that stress and anxiety can manifest in a lot of varied physical issues. Excessive thirst is one of them. If you’ve recently moved, gained or lost a pet, gained or lost a human family member (or roommate), or your cat has gone through a stressful situation like surgery or loud home construction, they might be feeling a little on edge. Other symptoms of stress in cats include the following:

  • Diarrhea
  • Vomiting
  • Bald patches from overgrooming or…
  • Greasy, raggedy looking, or matted coat from under-grooming
  • Runny nose
  • Goopy eyes
  • Eating non-food items like plastic, fabric, or fuzz from toys
  • Eating more or less than usual
  • Sudden weight loss or weight gain
  • If they pick up an illness or get an injury, recovery might be slower than expected (stress affects the immune system which helps with healing)

There are also behavioral issues associated with stress and anxiety:

  • Going to the bathroom outside of the litter box
  • A previously friendly cat might be more reactive (hissing, biting, scratching) or shy (hiding away from people)
  • Being extra-dependant on people or other animals for comfort
  • Spraying furniture
  • Playing less than normal
  • Meowing a lot
  • Pacing around the home

As you can see, there are a lot of symptoms here, and all of them are also signs of physical ailments. When you take your cat to the vet, first they’ll check for anything physical that might cause excessive thirst and any other of the above symptoms.

If your cat’s got a clean bill of physical health, the vet might suggest lifestyle changes to manage stress. You’ll need to pinpoint exactly what is causing the stress, then find ways to alleviate it. If you’ve just gotten a new pet, this reaction could be caused by introducing them too quickly. You might want to start the introduction process over, or give your older cat a “safe space” to get away from the new pet.

In some cases, you might just need to wait until your cat adjusts to their new normal (such as if your cat is upset when one spouse moves out after a separation). In this case, something like Feliway might be good to invest in, as many people find it keeps their cat calmer. I once had a cat with a very nervous disposition and he did much better with a Feliway diffuser running in the house.

Diabetes is a common medical condition that afflicts older, overweight cats. Diabetes can cause senior cats to drink more water than normal.

Diabetes mellitus

Diabetes will likely be one of the first things your cat’s checked for if you bring them in for excessive thirst. Diabetes is very common in older cats, and excessive thirst/frequent urination is a very common initial symptom that your cat has the disease. Insulin is a hormone the pancreas produces that regulates blood sugar after food is ingested. Diabetes occurs when your cat either stops producing enough insulin naturally, or for some reason, their body becomes resistant to insulin that it’s making, so it doesn’t do its job. So when your cat isn’t producing enough insulin, blood sugar spikes, which causes a wide array of symptoms.

  • Excessive thirst and urination are the top symptoms. Normally these symptoms are pretty dramatic – you won’t need to do the measuring cup test I mentioned earlier – you’ll KNOW when you’re cleaning the litter box 6 times a day (yes, when my diabetic cat was undiagnosed I was cleaning her litter box up to 6 times a day because she was flooding it).
  • Obesity. One cause of diabetes in senior cats is obesity. If your cat is obese and drinking a lot of water, diabetes will probably be your first assumption.
  • Sudden weight loss. On the other hand, some cats will drop weight very fast when they become diabetic. Your cat might be eating a normal amount, but they could feel like skin and bones. A condition caused by untreated diabetes, ketoacidosis, causes fat and protein to be broken down in spite of your cat eating plenty of food. This can cause your cat to technically starve even though they’re eating, and can lead to death if untreated.
  • Ravenous appetite. A cat with untreated diabetes isn’t able to get the energy and nutrients they need from food, so they’ll often feel like they need to eat more than they have to. Before my cat was diagnosed, if I even stepped foot into the kitchen she’d attack my legs to try and get me to feed her. I’ve never heard her meow so desperately than she did back then, she probably felt like she was starving. 🙁

Your vet will do a blood test to check your cat’s blood sugar. If it’s high, they’ll get a diabetes diagnosis.

Treatment for diabetes is two-fold: medication and diet. Most diabetic cats will need to use insulin. Lantus, I believe, is the most commonly prescribed. It was what I used and my cat had a really good reaction to it. This is injected under the skin with a syringe twice a day. It sounds intimidating, but you get used to it pretty quickly. I used to give my cat her insulin when she was eating, and I don’t think she even noticed when I jabbed her with the syringe.

Your vet will also prescribe a low-carb diet, and might prescribe a specialty diabetic cat food. If you’re rigorous about your cat’s diet and medication, eventually your cat may be able to get off of insulin and just stick to a diet. This is called “diet-controlled diabetes” or “remission”. Once your cat is diabetic they’ll always be diabetic – it’s probably something you’ll always need to keep an eye on, and it can easily come back if you slack on their diet. Thankfully though, diabetic cats can live long, healthy lives with treatment.

Chronic kidney disease can cause your cat to drink excessive amounts of water.

Chronic Kidney Disease (CKD)

Kidney issues are common in senior cats, and excessive thirst is an early symptom of chronic kidney disease. The kidneys provide a lot of functions for the body, particularly filtering blood and urine. When the kidneys age they might start declining in functionality, and CKD is one of the reasons why this happens. Before this condition is diagnosed and treated, there can be a number of symptoms associated with the buildup of toxins in the body.

In addition to excessive thirst, other symptoms of chronic kidney disease are the following:

  • Lethargy. This condition will make your cat feel generally yucky, so they likely won’t be as active or playful as they used to be.
  • Unkempt appearance. When your cat doesn’t feel well, they won’t be grooming as often. This will cause their fur to start looking greasy and disheveled.
  • Weight loss and loss of appetite. Since your cat won’t be feeling well, they won’t want to eat as much. It’s similar to when you have the flu and you feel so sick you don’t want to eat.
  • Frequent urination. Since your cat will be drinking more, they’ll also be peeing more. You’ll notice you’re cleaning the litter box a lot more than you were.
  • Anemia, or loss of red blood cells. If your cat is anemic, their gums will be a lighter pink than they should be, or even white in extreme cases.
  • Elevated blood pressure (hypertension). CKD cats will be urinating out more nutrients than they should be since they’re drinking so much water, and this can cause high blood pressure. Symptoms of high blood pressure include
    • Vision issues – their pupils will be dilated and won’t contract when you shine a light on them. If untreated this can lead to blindness.
    • Heart murmur
    • Untreated high blood pressure, even when it’s not related to CKD, can actually damage the kidneys. So untreated high blood pressure can damage the kidneys of a CKD cat very quickly.
    • Seizures
    • Fainting
    • Nose bleeds

If chronic kidney disease is suspected, your vet will do both a blood test and a urinalysis. While CKD can’t be cured, it can be managed and when caught early, your cat can live a completely normal life with this condition. First, your vet will want to modify your cat’s diet. Hills Kidney Care food is a popular one many vets recommend for CKD. Switching your cat to this diet can be tricky. It’s crucial for CKD cats to eat regularly, as lack of food, even for short periods, can be dangerous for cats wit this condition. However, some cats have trouble switching to a new diet. Make the transition to a new food a slow process, gradually adding in the kidney care food into what they normally eat. Remove more of the old food and add more of the new food every couple of days, until your cat is only eating the diet food.

Your vet will likely also give you a prescription to treat your cat’s hypertension, as well as a medication that will prevent your cat from urinating out important nutrients. If your cat is experiencing anemia, they might need a blood transfusion, accompanied by some additional medication or veterinary treatment to keep it from occurring. Since this is a condition that causes a lot of secondary medical issues, other medications might also be prescribed, such as anti-nausea medication.

Many cats, once the medication is prescribed and symptoms are controlled, can live many more years with CKD. It all depends on the severity of your cat’s case though. The worse the kidney damage, the worse the prognosis.

If your senior cat is drinking a lot of water, hyperthyroidism might be to blame.

Hyperthyroidism

Hyperthyroidism is a condition caused by an enlarged thyroid, causing the thyroid to overproduce hormones. This enlargement can be caused by a tumor, or sometimes for mysterious reasons your vet won’t be able to figure out. Thankfully, most cases of hyperthyroidism are very treatable.

Hyperthyroidism comes with a bunch of symptoms that, honestly, are pretty generic. Symptoms, aside from thirst and urination, include the following:

  • Weight loss
  • Increased appetite
  • Vomiting
  • Diarrhea
  • Hyperactivity

At your vet visit, if your vet suspects thyroid issues could be at play, he’ll gently palpate your cat’s throat to feel for the thyroid. If it seems enlarged, he’ll do blood tests to check thyroid hormone levels. Most cats with hyperthyroidism will have elevated levels of a hormone called T4. In rare cases, however, T4 will be normal even if the cat has hyperthyroidism. If your vet thinks your cat does have hyperthyroidism and T4 comes back normal, be sure to give them permission to do additional blood tests.

There are lots of different treatments for hyperthyroidism. Radioactive Iodine Therapy isn’t available everywhere, but it’s considered to be the best treatment for hyperthyroidism. In this treatment, your vet will inject your cat with radioactive iodine. This will be taken up into the thyroid through the bloodstream, and it can destroy the excess thyroid tissue without harming the healthy thyroid tissue. In many cases, hyperthyroidism is completely cured with this treatment after just a few weeks. In some cases, a second treatment is needed, and in rare cases, cats will need medication to actually boost thyroid hormone production if it gets too low.

Radioactive Iodine Therapy can be an actual cure, has few side effects, doesn’t require anesthesia, and is a quick and easy treatment with no upkeep (other than regular vet appointments). The downsides are the location and the cost. Since radioactive substances are being used, few veterinary facilities have the ability to do this treatment. Also, although the treatment is fast since your cat is radioactive during this time, they’ll need to be quarantined at the hospital for at least 5 days, so you won’t be able to see them during that time. The treatment, hospitalization, and travel costs if that’s required can make this extremely expensive, although it’s worth a try if you have the means.

Medication is the most common first step, since many clinics won’t be able to give your cat radioactive iodine therapy. Anti-thyroid drugs will reduce the amount of hormone released from the thyroid, which should resolve any symptoms caused by the overactive thyroid. While most cats do well on these medications, some cats have side effects so severe your vet will want to try something else. These side effects include vomiting and/or lack of appetite that leads to severe weight loss, fever, anemia, and lethargy. This medication is also available in a topical form if your cat doesn’t like pills.

In addition to medication, your vet might also want your cat to go on a low iodine diet. While this alone won’t fix an overactive thyroid, it’s believe that reducing the iodine in a cat’s diet can complement medical treatment. Hills Science Diet makes a thyroid care food vets really like.

Surgery to remove the thyroid is also an option. Since you’re removing the problem, this is a cure for hyperthyroidism. However, this requires anesthesia, which can be dangerous, and removing the thyroid completely can cause other medical issues, so it’s only done in rare cases, usually where medication or other therapies aren’t an option.


As you can see, there are a lot of reasons your elderly cat might be drinking a lot more water than usual. The most important thing is to see your vet. Increased thirst is not a normal part of aging, and the sooner you get your cat treated for whatever medical condition they have, the better their chances of getting back to normal.

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