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You may have wondered for a while if you're underweight. Or perhaps your friends or parents have mentioned it.
You can check by using our healthy weight calculator. If you're underweight, your doctor, practice nurse or school health visitor can give you help and advice.
There could be an underlying medical cause that needs to be checked out. Or perhaps you haven't been eating a healthy, balanced diet. That may be the result of stress or other emotional problems.
During your teenage years, your body is changing. Sometimes teenage girls can feel unhappy about these changes, but they are your body's way of preparing you for pregnancy in later life.
Whatever the situation, if you're concerned about your weight or your diet, the best thing to do is to tell someone. There's lots that can be done to help.
If our healthy weight calculator has told you that you may be underweight, think about why this might be.
Being underweight isn't good for you. It could cause:
If you're underweight, aim to gradually gain pounds until you get to a weight that's healthy for your height and age.
But it's important that you gain weight the right way. Chocolate, cakes, fizzy drinks and other high-calorie foods full of saturated fat and sugar are more likely to increase your body fat instead of your lean body mass.
If you'd like to put on some weight, eat foods that are healthy and packed with energy:
Learn more about healthy eating in Food and diet.
Even if you already know all about healthy eating, there may be other issues stopping you having a healthy diet.
If you feel anxious when you think about food, or you feel you may be using control over food to help you cope with stress, low self-esteem, or a difficult time at home or school, you may have an eating disorder.
People with eating disorders often say they feel the disorder is a way of keeping control over their lives. But that's an illusion: it's not them who is in control, but the eating disorder.
If you feel you may have an eating disorder, help is available. Tell someone – ideally your parents or carers, or another adult you trust.
Bear in mind that, if you are underweight because of an eating disorder, your treatment may include eating a diet that’s higher in sugar, fat and calories for a while.
Get informed about dodgy diet pills sold online.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.