The NHS has warned people taking medication for depression not to stop suddenly without speaking to a doctor, even if they feel better. The NHS says that while you may feel better, stopping citalopram without consulting your doctor could cause you to feel worse. And its guidance also reminds users about the six-week rule - which is how long you should give it to work.

The medication is part of a group of antidepressants called selective serotonin reuptake inhibitors, often just called SSRIs. It works by increasing serotonin levels in the brain, which helps to lift mood, emotions and regulate sleep.

The NHS explains that "it may take 1 or 2 weeks before citalopram starts to work on your symptoms. It usually takes between 4 and 6 weeks before you feel the full benefits."

It adds: "Do not stop taking citalopram after 1 or 2 weeks just because you feel it is not helping your symptoms. Give the medicine at least 6 weeks to work."

But it's not just this you need to be aware of. The NHS says: "Taking citalopram for panic attacks can sometimes make anxiety worse during the first few weeks of treatment. But this usually wears off after a few weeks. If it bothers you, speak to your doctor about it. A lower dose may help reduce your symptoms."

These common side effects of citalopram happen in more than 1 in 100 people. There are things you can do to help cope with them:

• Having a dry mouth
• Sweating a lot
• Being unable to sleep
• Feeling tired, weak or sleepy
• Headache
• Nausea

Serious side effects are rare and happen in less than 1 in 1,000 people. Book an appointment with your doctor if:

• you have changes in your periods, such as heavy bleeding, spotting or bleeding between periods
• you gain or lose weight without trying

Call a doctor or call 111 now if you:

• start bleeding from the gums or get bruises that appear without a reason or that get bigger
• have strong feelings of happiness, enthusiasm or excitement, or feeling restless and you cannot sit or stand still
• start coughing up blood or have blood in your pee
• have black or red poo, or blood in your vomit - these can be signs of bleeding from the gut

Call 999 or go to A&E now if:

• you have chest pain or pressure or shortness of breath
• you have a fit or seizure for the first time, or the seizures you have had in the past become more frequent
• you feel very dizzy, or pass out
• you have painful erections that last longer than 2 hours - this may happen even when you're not having sex
• you get bleeding from any cuts or nosebleeds that is very heavy or does not stop within 10 minutes
• you have thoughts about harming yourself or ending your life
• you get headaches, have trouble focusing, have memory problems, cannot think clearly, have weakness, have a seizure or fit, or lose your balance - these can be signs of low sodium levels

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to citalopram. 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

The medication can affect blood sugar stability, making it harder to manage. This means that if you have diabetes, you need to check your blood sugar levels more frequently during the first few weeks of treatment.

You may also need to change your diabetes medication while taking citalopram. Remember to always discuss your diabetes management plan with your doctor before starting this medication.

Citalopram is not suitable for some people. To make sure it's safe for you, tell your doctor if you:

• have ever had an allergic reaction to citalopram or any other medicine
• have a heart problem - citalopram can make your heart beat faster or cause an irregular heartbeat (arrhythmia)
• are trying to become pregnant, are already pregnant or breastfeeding
• have an eye condition called glaucoma - citalopram can increase the pressure in your eye
• have epilepsy or are having electroconvulsive treatment - citalopram may increase your risk of having a seizure
• have ever had a bleeding disorder such as haemophilia
• have ever had a stomach ulcer

If you feel better and want to stop, always tell your doctor and never just stop taking the medication. The NHS states: "If you have been feeling better for 6 months or more, your doctor may suggest coming off citalopram. They will probably recommend reducing your dose gradually over several weeks, or longer if you have been taking citalopram for a long time. This helps to stop any withdrawal symptoms you might get as a reaction to coming off the medicine."

These can include:

• feeling dizzy
• feeling sick
• numbness or tingling in the hands or feet
• trouble sleeping
• feeling agitated or anxious
• headaches
• shaking

For more information on Citalopram, visit the NHS website here. Call 116 123 to talk to Samaritans, or email jo@samaritans.org for a reply within 24 hours.

Text "SHOUT" to 85258 to contact the Shout Crisis Text Line, or text "YM" if you're under 19. If you're under 19, you can also call 0800 1111 to talk to Childline. The number will not appear on your phone bill.