A 15 month old should have at least 4 to 5 wet diapers per day although the amount of wet diapers per day that the 15 month old will have can vary from day to day.
If they are sweating a lot then the 15 month old may only have 3 to 4 wet diapers per day and if they are not sweating a lot or they are drinking more fluids then the 15 month old may have as many as 5 to 6 wet diapers per day.
The amount of wet diapers that is too few is less than 2 wet diapers per day for a toddler and less than 3 to 4 wet diapers for a baby of less than 2 years old.
As long as the toddler or baby is getting plenty of fluids and producing at least 2 to 4 wet diapers per day then they are most likely hydrated enough and are healthy.
If the toddler or baby has not had a wet diaper in 6 or more hours then it could be sign that they are dehydrated.
However my own 2 year old on really hot days will sometimes go 5 hours before he even pees and then can have a wet diaper by 6 hours and he's hydrated and healthy.
A 2 year old should have a minimum of 2 to 3 wet diapers per day if they are properly hydrated.
However if the weather is hot and the 2 year old is sweating a lot then they may only have 2 wet diapers and not more than that per day which is normal as long as they are drinking plenty of fluids.
During the hot weather the 2 year old will lose fluids through sweating so they won't be peeing as much because they won't produce as much pee.
My 2 year old normally has 3 to 4 wet diapers per day unless he's really drinking a lot of fluids and then sometimes he will have 5 to 6 wet diapers per day.
But during the summer months like now he usually only has 2 wet diapers per day and sometimes 3 wet diapers per day.
The amount of diapers your 2 year old will go through and have wet will vary from day to day and from season to season.
However the amount of wet diapers that a 2 year old will have per day depends on how much they drink and if they drink less they will pee less and if they drink more then they will pee more and have more wet diapers.
If the toddler or baby has no wet diaper within 4 to 6 hours then that is considered too long to go without a wet diaper.
Babies under 2 years old will usually pee more often when hydrated and should have a wet diaper every 1 to 2 hours or so.
If the diaper is still dry after 5 hours to 6 hours then it could be a sign of dehydration.
However if it's a toddler older than 2 years old then they can sometimes go 2 to 3 hours without wetting and then they will wet all at once.
You should take your toddler to the ER for dehydration if they are under 2 years old and they have had no wet diapers within 3 to 4 hours.
Or if the toddler is 2 or above and has had no wet diaper within 5 to 6 hours then you should take your toddler to the ER to be sure they are okay.
Or if you notice any of the signs below that your toddler is dehydrated then you should take the toddler to the ER.
Dry tongue and dry lips.
No tears when crying.
Fewer than six wet diapers per day (for infants), and no wet diapers or urination for eight hours (in toddlers).
Sunken soft spot on infant's head.
Sunken eyes.
Dry and wrinkled skin.
Deep, rapid breathing.
You should be concerned about a dry diaper if the baby under 2 years old has not peed within 3 to 4 hours and if the baby is older than 2 and has not peed within 6 hours then you should take the child to the hospital or urgent care.
If the baby seems weak or pale looking then take the child to the hospital as they could be dehydrated.
The length of time that is too long for no wet diaper depends on the age of the baby or toddler.
For babies under 2 years old if they haven't had a wet diaper within 3 hours then that would be too long for no wet diaper.
If the baby is 2 years old or above then longer than 6 hours or longer would be too long for no wet diapers.
Younger babies should pee more and have more wet diapers than an older baby or toddler.
Depending on age of the toddler some toddlers can have a dry diaper for an hour or as long as 3 to 4 hours.
And in some cases older toddlers such as 2 years old and 3 years old may have a dry diaper for as long as 5 to 6 hours and then suddenly pee at once.
This is usually because they are gaining some bladder control and are holding it in and then releasing the pee at once.
When properly hydrated a 2 year old boy should pee every 30 minutes to an hour.
Although it's also normal for some 2 year olds to pee only every few hours or so.
If the 2 year old has not peed within 6 to 8 hours and they are drinking enough then you should take the child to the doctor or urgent care to make sure they are properly hydrated.
Ideally a 2 year old baby should pee every 30 minutes to an hour.
Although it's also normal for a 2 year old baby to only pee every few hours or even every 3 hours.
As long as they are drinking enough fluids and having at least a few wet diapers per day then they are okay.
A 2 year old can go as long as 6 hours in some cases without a wet diaper.
However most often a 2 year old will only go as long as 2 hours to 3 hours without a wet diaper depending on how much they drink.
If it's hot outside then the 2 year old will sweat more and not produce as much urine and so they may go a few hours or even 4 hours without a wet diaper which is normal.
Some 2 year olds pee as often as every 20 to 30 minutes and some go as long as 1 hour to 2 hours and even 3 hours without peeing.
It is normal for a 2 year old boy to go 2 hours and sometimes even as long as 3 hours with a dry diaper before they pee.
My 2 year old sometimes goes 2 hour and sometimes as long as 3 hours before he wets his diaper.
At 2 years old they sometimes hold the pee in for a few hours and then once they feel their bladder filling up and get the urge to pee they then let lose.
If the 2 year old boy has not peed within 6 hours then I would be concerned about dehydration.
But sometimes toddlers and 2 year olds pee different amounts during the day.
Some days my 2 year old son pees every 30 minutes and has a wet diaper ever few hours and then some days he just does not pee as often and can have a dry diaper for 2 to 3 hours.
As long as you're keeping your toddler hydrated with water, juice etc then they should be okay.
But if the 2 year old boy has no wet diapers within 6 to 8 hours then I would take them to the doctor or urgent care to be checked out.
Some 2 year olds go through 4 to 5 diapers per day while some days some 2 year olds pee less and may only go through 2 to 4 diapers per day.