From our discussion it seems that your dog may be drinking more than it should or more than it usually does.

Drinking more than usual is a common medical sign in dogs, particularly in older dogs.

Drinking excessively is known as polydipsia(PD) and passing increased amounts of urine is called polyuria(PU). As you can imagine, these two things often go together and vets will often talk about this as PU/PD.

In most cases of PU/PD the pet is producing excessive amounts of dilute urine as the primary problem and having to drink more water to compensate for this.

You may only notice that your dog needs to go out more often or has accidents in the house, especially during the night. In these cases the accidents are due to the bladder being overstretched and not a behavioral problem. The dog simply cannot help it!  

Excessive drinking is defined as a dog drinking more than 100ml of water per KG of body weight per day. This can be hard to measure if dogs go outside and may drink elsewhere or if multiple dogs share water bowls. You may need to keep your dog in isolation for a few days to make an accurate measure of its water intake but this will be very useful for your vet. 

Measure how much water you put in the bowl each time you fill it, calculate a total over 3 full days ideally to account for daily variations. It is advisable to keep a very close eye on your dog when outside to avoid the pet drinking water from a different source e.g. a puddle. 

If you cannot measure your dog's water consumption and it appears well in all other respects, then a fresh urine sample  may help your vet decide if there is anything to be concerned about. A fresh sample is important as some components e.g. glucose in a diabetic case will reduce in the urine over time, possibly leading to misleading results.

A small sample can tell your vet a lot so don't worry about getting a big sample but be sure it is in a clean container. A marmalade jar and lid that has been cleaned and washed thoroughly(preferably in the dishwasher) will work well for this. Alternatively you can collect a urine sample pot from your local veterinary clinic beforehand

Many conditions can cause your dog to drink and urinate excessively (PU/PD). Here are some examples: 

Non pathological reasons

• These might be a change of diet, strenuous exercise or hot weather.

Medications

• Some commonly used medications can cause PU/PD, For instance steroids (often used for skin disease) or diuretics (often used to treat heart conditions)

Diabetes

• This is also frequently diagnosed in middle aged and older dog. Any suspicion of diabetes needs to be investigated as soon as possible. If diabetes is neglected, life threatening complications will develop over time.

Kidney disease

• This is a common cause of PUPD. This is most commonly age related and therefore frequently seen in older dogs. However, it can also be congenital (i.e. your dog was born with a problem) and so may occur at a young age. It may also result from consumption of toxic substances e.g. raisins and grapes or antifreeze.

If you suspect your pet has consumed anything that might be toxic consult your vet or your emergency out of hours service immediately. Do not wait to see if symptoms develop.

There are many other conditions where PU/PD may be one of the presenting signs, they vary in severity but some (for instance womb infections in un-neutered female dogs) can deteriorate very rapidly so you should not delay seeking an examination at your veterinary surgery if your dog appears to be drinking excessively. 

If increased thirst is accompanied by other changes such as reduced appetite, weight loss, tiredness, vomiting/diarrhoea etc. then that  increases the need for urgency.

The most important thing to know is that increased thirst without any obvious cause, or which persists over a period of days usually means that there is a medical problem and any increase in drinking beyond what you would normally expect should be looked into by your vet.

Blood and urine samples will often be required to discover the cause of the excessive thirst. This is best done as soon as possible during normal opening hours as many conditions that cause excessive urination and drinking are progressive and will become more serious if not addressed.

Older pets may often be dealing with multiple issues so a careful investigation by your vet will be necessary to make sure your pet gets the best treatment.

You should see a vet as an emergency as soon as possible if your dog has weakness, loss of appetite or any other deteriorating accompanying symptoms alongside the increased thirst.

If your dog has increased thirst with no other symptoms and seems well I recommend that you contact your vet at the first opportunity during normal working hours so this can be investigated