Lithium toxicity: warning signs, causes and what to do

Lithium is used to treat mood disorders such as mania and bipolar disorder, and sometimes as an add-on in depression. The NHS explains that the level of lithium in the blood is checked regularly because having too much, although rare, can cause side effects, and very high amounts can cause problems with the kidneys and other organs.

Lithium toxicity means the level in the blood has become too high for the body to tolerate. It can occur through taking too much, through changes in how the body clears lithium, or through the interaction of illness, dehydration or other medicines. The NHS describes the symptoms as signs of an emergency.

The NHS lists the following symptoms of lithium toxicity. It says to stop taking lithium straight away and to call 999 or go to A&E, and not to drive yourself but to ask someone to drive you or call an ambulance, bringing all your medicines with you.

• Stomach ache, feeling sick (nausea) and having diarrhoea

• Problems with your eyesight, such as blurred vision

• Feeling very thirsty, needing to pee more than normal, and lack of control over pee or poo

• Feeling lightheaded or drowsy

• Confusion and blackouts

• Shaking, muscle weakness, muscle twitches, jerks or spasms affecting the face, tongue, eyes or neck

• Difficulty speaking

Not every unpleasant effect is toxicity. The NHS says common side effects such as feeling sick, diarrhoea, a dry mouth or metallic taste, a slight tremor of the hands, and feeling tired or sleepy are usually mild and go away by themselves, and are more likely to happen when you start. It suggests simple meals, sips of water and sugar-free gum as coping measures.

A mild tremor that is bothering you or does not go away after a few days can be a sign that the dose is too high, and you should speak to your doctor. If tiredness or sleepiness does not improve within 2 weeks, the doctor may reduce the dose or increase it more slowly. The key is to tell your prescriber about changes rather than to ignore or adjust the dose yourself.

The NHS notes that lithium levels can be affected by illness. Infections and illnesses such as colds and flu can make you dehydrated, which affects lithium levels. It advises calling 111 if you have an illness that causes severe diarrhoea, vomiting, a high temperature or sweating, a urinary tract infection, or if you are not eating and drinking much.

Other medicines can change how lithium works. The NHS lists diuretics such as furosemide or bendroflumethiazide, NSAID painkillers such as ibuprofen, celecoxib or diclofenac, ACE inhibitors such as enalapril, lisinopril or ramipril, some antidepressants, antibiotics such as trimethoprim or metronidazole, and some epilepsy medicines such as carbamazepine. It says this is not a complete list. It also says there is not enough information to say that complementary medicines, herbal remedies and supplements are safe to take with lithium.

The NHS also advises not suddenly reducing salt intake, drinking plenty of fluids, particularly in hot weather or intense exercise, and being careful with alcohol, which causes the body to lose water.

When you start lithium you have a blood test every week to make sure the level is not too high or too low. Once the doctor is happy, you have a test every 3 to 6 months. Tests are timed 12 hours after the last dose, which is why lithium is usually taken once a day at night. If you have kidney problems, levels are monitored even more closely.

The NHS says there are two types, lithium carbonate and lithium citrate, which are absorbed differently, so you should not switch type unless your doctor recommends it. It also says that when stopping lithium, the dose must be reduced gradually over weeks or months, except if you have symptoms such as loss of appetite, eyesight problems or feeling very thirsty, in which case you stop and get medical help.

Rarely, lithium can cause a serious allergic reaction. The NHS says to call 999 if your lips, mouth, throat or tongue suddenly swell, you are breathing very fast or struggling to breathe, or your throat feels tight.