The symptoms of type 1 diabetes can develop very quickly (over a few days or weeks), particularly in children.

In older adults, the symptoms can often take longer to develop (a few months).

However, they should disappear when you start taking insulin and you get the condition under control.

The main symptoms of diabetes are:

• feeling very thirsty
• urinating more frequently than usual, particularly at night
• feeling very tired
• weight loss and loss of muscle bulk
• itchiness around the genital area, or regular bouts of thrush (a yeast infection)
• blurred vision caused by the lens of your eye changing shape
• slow healing of cuts and grazes

Vomiting or heavy, deep breathing can also occur at a later stage. This is a dangerous sign and requires immediate admission to hospital for treatment.

You should visit your GP immediately if you think you may have diabetes.

When to seek urgent medical attention

You should seek urgent medical attention if you have diabetes and develop:

• a loss of appetite
• nausea or vomiting
• a high temperature
• stomach pain
• fruity smelling breath – which may smell like pear drops or nail varnish (others will usually be able to smell it, but you won't)

Hypoglycaemia (low blood glucose)

If you have diabetes, your blood glucose levels can become very low. This is known as hypoglycaemia (or a "hypo"), and it's triggered when injected insulin in your body moves too much glucose out of your bloodstream.

In most cases, hypoglycaemia occurs as a result of taking too much insulin, although it can also develop if you skip a meal, exercise very vigorously or drink alcohol on an empty stomach.

Symptoms of a "hypo" include:

• feeling shaky and irritable
• sweating
• tingling lips
• feeling weak
• feeling confused 
• hunger
• nausea (feeling sick)

A hypo can be brought under control simply by eating or drinking something sugary.

If it isn't brought under control, a hypo can cause confusion, slurred speech and, eventually, unconsciousness.

In this case, an emergency injection of a hormone called glucagon will be needed. Glucagon increases the glucose in your blood.

Hyperglycaemia (high blood glucose)

As diabetes occurs as a result of your body being unable to produce any, or enough, insulin to regulate your blood glucose, your blood glucose levels may become very high. This happens because there's insufficient insulin to move glucose out of your bloodstream and into your cells to produce energy.

If your blood glucose levels become too high, you may experience hyperglycaemia. The symptoms of hyperglycaemia are similar to the main symptoms of diabetes, but they may come on suddenly and be more severe. They include:

• extreme thirst
• a dry mouth
• blurred vision
• drowsiness
• a need to pass urine frequently 

Left untreated, hyperglycaemia can lead to diabetic ketoacidosis. This is a serious condition, where the body breaks down fat and muscle as an alternative source of energy. This leads to a build-up of acids in your blood, which can cause vomiting, dehydration, unconsciousness and even death.

The Diabetes UK website has more information about diabetes symptoms.