If diabetes isn't treated, it can lead to a number of different health problems. High glucose levels can damage blood vessels, nerves and organs.

Even a mildly raised glucose level that doesn't cause any symptoms can have damaging effects in the long term.

Heart disease and stroke

If you have diabetes, you're up to five times more likely to develop heart disease or have a stroke.

Prolonged, poorly controlled blood glucose levels increase the likelihood of developing atherosclerosis (furring and narrowing of your blood vessels).

This may result in a poor blood supply to your heart, causing angina (a dull, heavy or tight pain in the chest). It also increases the chance that a blood vessel in your heart or brain will become completely blocked, leading to a heart attack or stroke.

Nerve damage

High blood glucose levels can damage the tiny blood vessels of your nerves. This can cause a tingling or burning pain that spreads from your fingers and toes up through your limbs. If the nerves in your digestive system are affected, you may experience nausea, vomiting, diarrhoea or constipation.

Retinopathy

Retinopathy is where the retina (the light-sensitive layer of tissue) at the back of the eye is damaged. Blood vessels in the retina can become blocked or leaky, or can grow haphazardly. This prevents the light from fully passing through to your retina. If it isn't treated, it can damage your vision.

The better you control your blood sugar levels, the lower your risk of developing serious eye problems. Having an annual eye check with a specialist (an ophthalmologist or optometrist) can help pick up signs of a potentially serious eye problem early so that it can be treated. 

Read about diabetic eye screening.

If it's caught early enough, diabetic retinopathy can be managed using laser treatment. However, this will only preserve the sight you have, rather than make it better.

Kidney disease

If the small blood vessels in your kidney become blocked and leaky, your kidneys will work less efficiently.

In rare, severe cases, this can lead to kidney failure and the need for dialysis (treatment to replicate the functions of the kidneys). In some cases, a kidney transplant may be necessary.

Foot problems

Damage to the nerves of the foot can mean that small nicks and cuts aren't noticed, which can lead to a foot ulcer developing. About 1 in 10 people with diabetes get a foot ulcer, which can cause serious infection.

If you develop nerve damage, you should check your feet every day and report any changes to your doctor, nurse or podiatrist. Look out for sores and cuts that don't heal, puffiness or swelling, and skin that feels hot to the touch. You should also have a foot examination at least once a year.

Read more about foot care and diabetes.

Sexual dysfunction

In men with diabetes, particularly those who smoke, nerve and blood vessel damage can lead to erection problems. This can usually be treated with medication.

Women with diabetes may experience:

• a reduced sex drive (loss of libido)
• reduced pleasure from sex
• vaginal dryness
• a reduced ability to orgasm
• pain during sex

If you experience a lack of vaginal lubrication, or you find sex painful, you can use a vaginal lubricant or a water-based gel.

Miscarriage and stillbirth

Pregnant women with diabetes have an increased risk of miscarriage and stillbirth. If your blood sugar level isn't carefully controlled immediately before and during early pregnancy, there's also an increased risk of the baby developing a serious birth defect.

Pregnant women with diabetes will usually have their antenatal check-ups in hospital or a diabetes clinic. This allows doctors to keep a close eye on their blood sugar levels and control their insulin dosage more easily.

The Diabetes UK website has more information about diabetes complications.