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.
Find out more about Legionnaires' disease, an uncommon but serious lung infection you can get from inhaling droplets of water containing bacteria that cause the infection.
Read about lichen sclerosus, a skin condition that mainly affects the skin of the genitals. Find out about symptoms, causes, treatments and when to see a GP.
Find out more about limping in children, which is usually caused by something minor like a sprain or strain.
Find out about lipoedema, an abnormal build-up of fat in your legs and sometimes arms, including what the symptoms are, when to get medical help and what treatments are available.
Find out about lipomas, which are soft, fatty lumps that grow under your skin. They're harmless and do not usually need any treatment.
Find out about the different types of liver disease and their causes . Find out the symptoms of liver disease, 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.
A low sex drive (loss of libido) can affect both men and women. Find out what can cause it, when to get help and how it can be treated.
Find out about low blood sugar (hypoglycaemia), including what the symptoms are, the causes, how to treat it and how to prevent it.
Find out about low sperm count, including symptoms, tests and treatments.
NHS information about lumps and swellings. Find out about different types of lumps and what causes them, and when to get medical advice.
Read NHS information on Lyme disease, which is a bacterial infection spread to humans by infected ticks.
Read about labyrinthitis and vestibular neuritis (also known as vestibular neuronitis), including advice about symptoms, when to get medical help and treatment.
Find out about lactose intolerance, what the symptoms are, what the treatments are, what tests can find out if you have it, and what causes it.
Find out more about laparoscopy, a type of keyhole surgical procedure that uses small cuts to perform surgery inside the tummy and pelvis.
Read about laryngeal cancer, including the symptoms, causes, treatments and outlook.
Find out 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.
Find out more about a lazy eye (amblyopia), a condition where the vision in 1 eye does not develop properly.
Find out about leg cramps, a common condition where the muscles in the leg suddenly become tight and painful.
Find out about leptospirosis infection, including what causes it, what the symptoms are, where to get help, how it's treated, and how to avoid getting it.
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.
Find out about long-sightedness, what the symptoms are, what tests you can have, how it is treated, and what causes it.
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.
Find out about lumbar punctures, including why they’re done, what happens during the procedure, side effects, how to help your recovery, and possible complications.
Lung cancer is one of the most common and serious types of cancer. More than 43,000 people are diagnosed with the condition every year in the UK.
Find out about lupus (systemic lupus erythematosus), including causes, symptoms, 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.
Find out 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's 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.
Find out what laser eye surgery and lens surgery are, why they're done, what happens during the operation and possible complications.
Find out about lung health checks, who can get them and what will happen at your appointment.
Find out about liver cancer, including the symptoms, causes, tests, treatments, and where to get support.