Four health problems you don't know you have until too late

... and the routine tests you should be having

Young adult man suffering from severe heartache.

Modern medicine can cure a lot of ills, but some diseases are hard to identify until it's too late. Here are four health issues that we can suffer from, without being aware that there's a problem.

See also: Five cancers you're more prone to over the age of 50

See also: Men and cancer - six symptoms you should never ignore

1. High blood pressure
Headaches, dizziness, a red complexion - you would know if you had high blood pressure, right? Wrong. Lots of people have dangerously high blood pressure without knowing it.

Having high blood pressure - or hypertension as doctors call it - can be fatal. It dramatically increases your risk of strokes and kidney and heart disease. Because it doesn't cause symptoms, your blood pressure can keep creeping up until it causes major problems.

Worryingly, as many as seven million people in the UK are believed to be living with high blood pressure – and the only way to ensure that you're not one of them is to get checked.

Health experts recommend that everyone over 40 gets their blood pressure taken by a nurse or doctor as part of a yearly health check. You can also buy a blood pressure monitoring device to check your numbers at home.

- Ten surprising ways to lower your blood pressure

2. Sleep apnoea
Sleep apnoea is a common condition which causes the tissues of the throat to relax and block the airways at night. The resulting lack of oxygen triggers you to wake up, often with a loud snort or gasp, before falling asleep again. This can happen hundreds of times during the night without you realising. It can cause a dry mouth, headaches and tiredness, but not all sleep apnoea sufferers are aware of the problem, particularly if they sleep alone.

Overweight men aged between 60 and 65 and smokers are most at risk. As it can be hard to identify, as many as one-in-three sufferers may not be aware that they have a problem. If you often feel tired, it's worth speaking to your doctor and getting your blood pressure checked at the same time.

Lifestyle changes and wearing a mask that delivers oxygen during the night - a Continuous Positive Airway Pressure (CPAP) device, can help.

3. Glaucoma
Glaucoma is the name given to a group of eye conditions that cause permanent sight loss by damaging your optic nerve. Because most types of glaucoma have no symptoms, it's important to have your eyes tested regularly, particularly as you get older. While glaucoma can affect people of all ages, including babies and young children, it is most common in adults in their 70s and 80s.

Glaucoma affects your peripheral vision first – and because this is not as sensitive as your central vision, you may not be aware that you have a problem. Both eyes are usually affected, although it may be worse in one eye. Laser surgery and treatment with drops can often prevent glaucoma causing sight loss - without treatment, it can eventually lead to blindness.

4. Lung cancer
Lung cancer is usually symptomless at the beginning - and even in the later stages, many of the signs are easy to mistake for something else. Common signs include a stubborn cough that lasts several weeks, repeated chest infections, coughing up blood, and unexplained weight loss. Because of this, many people are only diagnosed once the cancer has spread further, which makes it harder to treat. According to Cancer Research UK, 'emergency presentation' is the most common route to diagnosing lung cancer.

Lung cancer is the third most common cancer in the UK (2014) and the majority of cases (89%) are linked to lifestyle factors including smoking, certain occupational exposures (13%), and ionising radiation (5%). If you are a smoker, never ignore a cough that won't go away or coughing up blood. It's also important to be aware that even someone who has never smoked can get lung cancer.

- Seven surprising lung cancer symptoms