Read about labial fusion. This is when the small inner lips around the entrance to the vagina become sealed together. It's fairly common in girls under the age of 7. It usually gets better on its own, but can be treated with creams or, very rarely, surgery.
Find out about Lambert-Eaton myasthenic syndrome, a rare condition affecting the nerves that causes muscle weakness and other symptoms.
A lactate dehydrogenase (LDH) test measures the amount of LDH in the blood.
Read about Legionnaires' disease, an uncommon but serious lung infection you can get from inhaling droplets of water that contains Legionella bacteria.
Lichen sclerosus is a long-term skin condition that mainly affects the skin of the genitals. It usually causes itching and white patches to appear on the affected skin.
If a child is limping, the limp is usually due to a minor injury such as a sprain or splinter. But if there's no obvious cause, see your GP.
Read about lipoedema, which is an abnormal build-up of fat in your legs and sometimes arms. Find out what the symptoms are, when to get medical help and what treatments are available.
Read about lipomas, which are soft, fatty lumps that grow under your skin. They're harmless and do not usually need any treatment.
Read about the different types of liver disease and what causes them. Find out what the symptoms of liver disease are, when to get medical help and what you can do to prevent it.
Find out what local anaesthetics are, when they're used, and what the possible side effects are.
NHS information about long QT syndrome, including symptoms, causes and treatments.
Loss of libido, or reduced sex drive, is a common problem in men and women. Find out what can cause it and where to get help.
Find out about the symptoms of low blood sugar (hypoglycaemia), what causes it, how it can be treated and how to prevent it.
Find out about the causes of a low sperm count, how to get tested, and what the main treatments are to help to conceive.
NHS information about lumps and swellings. Find out about different types of lumps and what causes them, and when to get medical advice.
Lyme disease is a bacterial infection spread to humans by infected ticks.
Read about labyrinthitis (also known as vestibular neuritis or vestibular neuronitis), including advice about symptoms, when to get medical help and treatment.
Lactose intolerance is a common digestive problem where the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products.
Laparoscopy is a type of surgical procedure that allows a surgeon to access the inside of the abdomen (tummy) and pelvis without having to make large incisions in the skin.
Read about laryngeal cancer, including the symptoms, causes, treatments and outlook.
Read about laryngitis, which is when your voice box becomes irritated or swollen. Symptoms of laryngitis usually come on suddenly and get worse during the first 3 days.
Find out about different types of laxatives, how they work, how to choose the right one and how long to take them for. Also, find out about the possible side effects of laxatives.
A "lazy eye" is a childhood condition where the vision does not develop properly. It's known medically as amblyopia.
Read about leg cramps, a common condition where the muscles in the leg suddenly become tight and painful.
Leptospirosis is an infection that's spread by animals. It's rare in the UK.
Leukoplakia is a white patch that develops in the mouth. The condition is usually painless but is closely linked to an increased risk of mouth cancer.
Find out about lichen planus, a non-infectious, itchy rash that can affect many areas of the body.
NHS information and advice about listeriosis, including how you catch it, what the symptoms are and how you can avoid it.
Understand more about liver cancer, it's symptoms, when to get medical help, testing and diagnosis, treatment and where to find help and support.
Find out about liver transplant, an operation to remove a diseased or damaged liver and replace it with a healthy one.
Find out about the symptoms, causes and treatments for long-sightedness.
Find out about low blood pressure (hypotension), including what the symptoms are, when to get your blood pressure checked and treatments for low blood pressure.
Lumbar decompression surgery is a type of surgery used to treat compressed nerves in the lower (lumbar) spine. It's only recommended when non-surgical treatments haven't helped.
Read about having a lumbar puncture, including when it’s needed and how to recover after having one.
Lung cancer is one of the most common and serious types of cancer. Around 44,500 people are diagnosed with the condition every year in the UK.
Find out about lung transplants, including when it's needed, the different types of transplant, what the procedure involves and the associated risks.
Lupus (systemic lupus erythematosus) causes symptoms like joint pain, tiredness and skin rashes. Find out about treatment and how you can ease your symptoms.
Read about lymphoedema, a long-term condition that causes swelling in the body's tissues. It usually develops in the arms or legs.
NHS information about low white blood cell count. It usually means your body is not making enough white blood cells and can increase your risk of getting infections.
A change in your sense of smell can be unpleasant and affect how things taste. But it is not usually serious and may get better in a few weeks or months.
A learning disability affects the way a person learns new things throughout their lifetime.