Like all medicines, dexamethasone can cause side effects, although not everyone gets them.
Side effects are less likely if you're on a lower dose (less than 6mg a day).
Common side effects
These common side effects of dexamethasone happen in more than 1 in 100 people. There are things you can do to help cope with them:
Weight gain
Try to eat a healthy balanced diet without increasing your portion sizes. Regular exercise will also help to keep your weight stable.
Indigestion
Take dexamethasone with a meal or snack to reduce the chances of stomach problems. It may also help to avoid rich or spicy food.
If these symptoms carry on, speak to your doctor. They may give you an extra medicine to protect your stomach.
Sleep problems
Take dexamethasone in the morning so the levels of dexamethasone in your body are low at bedtime. If you take dexamethasone more than once a day try taking your last dose before 6pm.
Avoid having a big meal, smoking, or drinking alcohol, tea or coffee in the evening. Try not to watch television or use your mobile phone before going to bed. Instead, try to relax for an hour before bedtime.
Mild mood changes
Dexamethasone can affect your mood in different ways. Talk to your doctor if you're finding it hard to cope.
Talk to your doctor or a pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Serious side effects
Serious side effects are more likely with higher doses (6mg a day or more) or if you take dexamethasone for more than a month.
Speak to a doctor if you get "moon face" (a puffy, rounded face) and weight gain in your upper back or belly. This happens gradually and can be a sign of Cushing's syndrome.
Call a doctor or call 111 now if you get:
- a high temperature, chills, a very sore throat, ear or sinus pain, a cough, coughing up more mucus (phlegm) or a change in colour of your mucus, pain when you pee, mouth sores or a wound that will not heal – these can be signs of an infection
- a very upset stomach or you're being sick (vomiting), very bad dizziness or passing out, muscle weakness, very tired, mood changes, loss of appetite and weight loss – these can be signs of adrenal gland problems
- sleepy or confused, very thirsty or hungry, a need to pee more often than usual, flushing, breathing quickly or breath that smells like fruit – these can be signs of high blood sugar (hyperglycaemia)
- muscle pain, weakness or cramps, or your heartbeats suddenly become more noticeable (heart palpitations) – these can be signs of low potassium levels
- severe stomach pain, severe back pain, severe upset stomach or you're being sick (vomiting) – these can be signs of pancreas problems
- breathlessness
- swelling in your arms or legs
- changes in your eyesight
- any bruising or bleeding that is not normal
- red or black poo
Immediate action required: Call 999 or go to A&E if:
- you have black or dark brown vomit or you're vomiting blood
Mood changes
You may notice mood changes and mental health problems while taking dexamethasone.
Talk to your doctor or call 111 if:
- you're feeling high, or have moods that go up and down
- you're feeling depressed
- you're feeling anxious
- you have problems sleeping
- you have difficulty in thinking, or are feeling confused and forgetting things
- you're feeling, seeing or hearing things that do not exist (hallucinations)
- you notice changes in the way you usually behave
The higher the dose, the more intense the mood changes can be.
Immediate action required: Call 999 or go to A&E if:
- you have thoughts about harming yourself or ending your life
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to dexamethasone.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Long-term side effects
If you take dexamethasone for several months it can make your bones weaker and more likely to break (osteoporosis) and you can get eyesight problems.
If you have diabetes, dexamethasone can affect blood sugar control. Your doctor may need to adjust your diabetes treatment while you take this medicine and again after you stop.
Long-term side effects in children and teenagers
Dexamethasone can cause slower growth in children and teenagers if they take it for a long time.
Your child's doctor will monitor their height and weight carefully for as long as they're taking dexamethasone. This will help them spot any slowing down of your child's growth and change their treatment if needed.
Even if your child's growth slows down, it does not seem to have much effect on their eventual adult height.
Talk to your doctor if you're worried. They'll be able to explain the benefits and risks of giving your child dexamethasone.
Other side effects
These are not all the side effects of dexamethasone. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.