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Bipolar disorder is a long-term mood condition. It brings episodes of high mood (mania or hypomania) and episodes of depression, usually with stable spells between. Bipolar I involves at least one full manic episode. Bipolar II involves hypomania and depression. Cyclothymia is a milder, persistent pattern lasting at least two years.
A psychiatrist usually makes the diagnosis after a detailed history, normally following a GP referral. In England, NICE recommends lithium as the first-line long-term treatment. For bipolar depression it recommends specific options rather than an antidepressant on its own. It also recommends a psychological therapy built for bipolar disorder.
NICE estimates that bipolar I affects about 1% of adults and bipolar II about 0.4%. The peak age of onset is 15 to 19.
"Rapid cycling" means four or more mood episodes in a year. NICE says it should be treated like other bipolar disorder. "Mixed" states combine manic and depressive symptoms at once.
DSM-5 versus ICD-11. A 2021 comparison of the two main diagnostic manuals rated bipolar I and II as essentially identical across the two. The main difference is mixed states: ICD-11 has a separate "mixed episode", while DSM-5 uses a "mixed features" label.
The NHS lists these signs of high mood:
Low mood looks like any depression, including, for some, suicidal thoughts. The HSE notes that people may not notice their own changes during a high.
The difference is the history of highs. A bipolar depressive episode can look exactly like any other depression, which is why it is so often missed.
NICE tells GPs to ask anyone with depression about past periods of overactivity or disinhibited behaviour. If that lasted four days or more, NICE says to consider a specialist referral. Highs may not come up unless someone asks. In cyclothymia, the NHS notes, highs can feel nice, so people may not realise anything is wrong.
The delay is real. A 2017 meta-analysis pooled 27 studies covering 9,415 patients. The average gap between onset and first management was 5.8 years. "Management" meant diagnosis, first treatment or first hospital admission. The studies varied widely, and the gap was longer when diagnosis was the end point. Treat it as a rough average.
Some people are diagnosed with depression first. A 2017 meta-analysis of 56 studies followed people with major depression for 12 to 18 years on average. Nearly a quarter (22.5%) went on to develop bipolar disorder.
If you have depression with no history of highs, our guide to what actually works for depression is the better starting point.
These conditions overlap and can coexist, and NICE lists both among the diagnoses to consider. Telling them apart can be genuinely difficult.
ADHD. A 2021 meta-analysis of 71 studies found about 1 in 13 adults with ADHD also had bipolar disorder (7.95%). Nearly 1 in 6 adults with bipolar disorder had ADHD (17.11%). Rates varied a lot between studies.
The clearest difference is time course. NICE's ADHD guideline describes symptoms that began in childhood and persisted throughout life. A bipolar assessment looks for distinct episodes that differ from a person's usual self. Our guide to telling adult ADHD from burnout covers the childhood-history question.
It matters for treatment. A Swedish registry study followed 2,307 adults with bipolar disorder who started methylphenidate. Without a mood stabiliser, mania was more frequent in the next three months (hazard ratio 6.7, 95% CI 2.0 to 22.4). With a mood stabiliser, mania risk was lower afterwards (0.6, 0.4 to 0.9). This was observational. NICE's ADHD guideline asks for slower dose changes and closer monitoring when bipolar disorder is also present. Our explainer on what ADHD stimulants actually do covers the drugs.
Borderline personality disorder (BPD). A 2016 meta-analysis found BPD in 21.6% of people with bipolar disorder. It found bipolar disorder in 18.5% of people with BPD. The authors concluded the differences between the two matter more than the similarities.
The NHS describes BPD mood swings over a short space of time, such as despair and then feeling reasonably positive a few hours later. Bipolar mood episodes usually last days or weeks.
There is no blood test or scan for bipolar disorder. Diagnosis rests on a careful history.
NICE says GPs should not use questionnaires to identify bipolar disorder. The specialist will ask about your mood history, triggers and family history. NICE encourages inviting a family member or carer, who may remember highs you do not. Tests may look for physical causes such as an underactive or overactive thyroid.
NICE guideline CG185 covers England and was updated in September 2025. HSE guidance for Ireland describes the same main medicines: lithium, anticonvulsants and antipsychotics.
If you are not already on a mood stabiliser or antipsychotic, NICE recommends an antipsychotic: haloperidol, olanzapine, quetiapine or risperidone. Lithium, then valproate, can be added. NICE also advises calm surroundings and delaying big decisions. It says not to offer lamotrigine for mania.
For moderate or severe bipolar depression, NICE's first options are fluoxetine combined with olanzapine, or quetiapine alone. Olanzapine alone or lamotrigine alone are alternatives. An antidepressant on its own is not among them. If mania develops on an antidepressant alone, NICE says to consider stopping it.
The concern is a switch into mania. A Swedish registry study followed 3,240 people with bipolar disorder. Mania risk rose in the next three months on an antidepressant alone (hazard ratio 2.83, 95% CI 1.12 to 7.19). With a mood stabiliser, there was no clear rise. This too was observational. The HSE says antidepressants alone may lead to relapse, so they are often used with a mood stabiliser. Our explainer on what SSRIs actually do covers the drugs.
NICE calls lithium the most effective long-term treatment for bipolar disorder and recommends it first-line. If lithium does not work, is not tolerated or is not suitable, NICE suggests an antipsychotic such as asenapine, aripiprazole, olanzapine, quetiapine or risperidone. Stopping any of these should be planned and gradual. NICE advises monitoring mood for two years after medication stops entirely.
Valproate (brands include Epilim and Depakote) can seriously harm an unborn baby. The UK regulator, the MHRA, says around 1 in 9 exposed babies (11%) have a birth defect. About 3 or 4 in 10 children may have problems with early development.
The MHRA and HPRA both say not to stop valproate without talking to your specialist.
NICE lists lamotrigine for bipolar depression, not mania. NICE says to contact your doctor immediately if a rash appears while the dose is being increased. In the US it is FDA-approved for maintenance treatment of bipolar I, with a boxed warning about serious rashes.
NICE asks for weight, blood pressure, blood sugar and cholesterol checks before and during antipsychotic treatment. Our guide to what antipsychotics actually do explains why their side effects differ so much.
To prevent relapse, NICE recommends a structured therapy designed for bipolar disorder, delivered individually, in a group or with family. It should follow a published, evidence-based manual. These programmes cover:
For bipolar depression, NICE suggests a bipolar-specific therapy, or CBT, interpersonal therapy or behavioural couples therapy. The therapist should have experience with bipolar disorder. NICE also recommends support programmes for carers.
Sleep matters in both directions. "Not needing much sleep" is a sign of high mood. The NHS also lists lack of sleep, stress and being too busy as possible triggers. It suggests:
NICE recommends a written plan listing your triggers, early warning signs and who to call. In Ireland, the HSE suggests a Wellness Recovery Action Plan through your CMHT.
Lithium works well, but the gap between an effective level and a harmful one is narrow. Your team sets the target. This is NICE's outline only.
The NHS says the blood test is usually taken 12 hours after your last dose. You should get a lithium record book and an alert card.
Get help urgently if you develop signs of lithium toxicity. The NHS lists sickness and diarrhoea, blurred vision, unusual thirst, drowsiness, confusion, marked shaking or twitching, and difficulty speaking. Call 999 or go to A&E (112 or 999 in Ireland).
Seek advice during any vomiting, diarrhoea or acute illness, and keep fluids up when sweating. NICE advises against over-the-counter anti-inflammatories such as ibuprofen. Some diuretics, blood pressure medicines and antidepressants also change lithium levels, so tell your pharmacist everything you take.
No, according to the NHS, but treatment can help manage it. Stable periods can last weeks, months or years.
The highs are less severe, but it is not simply "bipolar lite". The US National Institute of Mental Health notes that many people with bipolar II spend long periods in low-grade depression.
Talk to your prescriber first. NICE and the NHS warn that stopping suddenly raises the risk of relapse. If lithium is stopped, it should be reduced gradually under supervision.
This article is general information, not medical advice. It does not replace an assessment or a conversation with your GP, psychiatrist or pharmacist. Do not start, stop or change any medicine without talking to your prescriber.
Reviewed by: Proco Team
Last updated: November 2026