How can I tell if my child is sick?
Is my child very sick?
Healthy young children have on average 12 infections each year. These are a normal part of childhood. As a parent or caregiver you deal with these but you may worry about missing a serious illness.
 
There is no foolproof system to tell you whether or not your child is seriously ill. 
Knowing your child and seeing a change in your child’s behaviour could be the most important clue. 
What do you do if you think your child is sick?
Depending on the circumstances you may decide to: 
see your GP (general practitioner) 
go to an after-hours medical centre 
dial  for urgent medical help 
You should stay calm and explain why you are worried about your child. Ask for your child to be seen by a doctor.
 
If you are waiting to be seen and think that your child is getting sicker, calmly explain again why you need your child to be seen soon.
 
In some circumstances it might be better to dial urgent medical help  for help rather than travel to the doctor using your own car.
Symptoms
The following is a list of some of the symptoms that mean your child has a significant health problem. See a doctor if your child:
has an unusual colour – they are very pale or have blue tongue and lips 
has a worrying rash especially one that does not go away when you press on it 
is very sleepy or drowsy 
has an unusual high-pitched cry 
has trouble breathing, has noisy breathing or is breathing fast 
complains of a stiff neck or light hurting their eyes 
has a severe headache 
refuses to drink - even small sips  
is not passing urine 
passes urine that is very dark or has blood in it 
vomits a lot – and cannot keep sips of replacement drinks down 
vomits yellow-green fluid (bile) 
vomits blood – this may be red or brown or look like coffee grounds if it is not fresh 
has black tar-like stools or blood in the bowel motions 
has frequent and watery bowel motions (diarrhoea) 
has a fever that lasts for more than two days 
is in pain 
is not interested in surroundings (lethargic)  
is getting sicker or is not improving after two days
What about young babies?
Young babies (less than three months old) need a more cautious approach. 
 
If your child is under three months old and you are worried about them, they should be checked by a doctor, even if they do not have one of the above symptoms. You should trust your instinct.
Source: http://www.kidshealth.org.nz
Other links:
Creating a Reader-Friendly Home 
Fitness and Your 4- to 5-Year-Old 
Misbehave and you pay