Febrile seizures (febrile convulsions) are fits that can happen when a child has a fever. They most often happen between the ages of 6 months and 3 years.
Find out what female genital mutilation (FGM) is, why and where's it carried out, what the health risks are, and where to get help and advice.
Read about flat feet (fallen arches), including why they happen, whether they're serious and how they can be treated.
Read about fluoride - a naturally occurring mineral found in toothpaste, drinking water and some foods that can help to prevent tooth decay.
Find out about foetal alcohol syndrome, a range of mental and physical problems that can affect children whose mothers drink alcohol while they're pregnant.
Find out about the link between certain artificial food colours and hyperactivity in children.
A food intolerance is difficulty digesting certain foods and having an unpleasant physical reaction to them.
Find out about foot drop, a muscular weakness or paralysis that makes it difficult to lift the front part of your foot and toes.
Find out about fabricated or induced illness (FII), which is a rare form of child abuse where a parent or carer exaggerates or deliberately causes symptoms of illness in the child.
Read about fainting (syncope), a sudden temporary loss of consciousness that usually results in a fall.
Anyone can have a fall, but older people are more vulnerable and likely to fall, especially if they have a long-term health condition.
A femoral hernia is an uncommon type of hernia. It's estimated that only about 1 in every 20 groin hernias are femoral hernias, and the rest are inguinal hernias.
Read about the different types of fibroids and why they develop. Find out when to see a GP if you have fibroids and how they're treated.
Fibromyalgia, also called fibromyalgia syndrome (FMS), is a long-term condition that causes pain all over the body.
Find out what to do in emergency situations such as anaphylaxis, bleeding, burns and scalds, choking, drowning, electrocution, fractures, heart attacks, poisoning, shock and stroke.
Flatulence is passing gas from the digestive system out of the back passage. It's more commonly known as "passing wind", or "farting".
Flu is a common infectious viral illness spread by coughs and sneezes. It can be very unpleasant, but you'll usually begin to feel better within about a week.
A food allergy is when the body's immune system reacts unusually to specific foods. Allergic reactions are often mild, but they can sometimes be very serious.
Read about the symptoms and causes of food poisoning and what you should do if you get it. It's not usually serious and most people get better within a week without treatment.
Find out what frontotemporal dementia is, what the symptoms are, how it's treated, and what the outlook is.
Read about frostbite, how it's caused and how to prevent it. Also find out what to do if you have frostbite and when to get medical assistance.
Frozen shoulder means your shoulder is painful and stiff for months, sometimes years. Find out about the main symptoms, treatments and causes.
Read about fungal nail infections, including the symptoms, causes and treatments.
Find out about floaters, which are small shapes that some people see floating in their field of vision.
NHS Fitness Studio: free online fitness videos, aerobics vidoes, strength and resistance videos, pilates and yoga videos and more.
Feeling sick (nausea) is common and usually goes away on its own. Find out about some things you can try that might help and what might be causing it.
Choose which area of your foot hurts most to read about treatments, when to get medical help and possible causes of foot pain.