Lithium Test

The lithium test, also known as a blood lithium test or serum lithium test, measures the amount of lithium in the blood. Lithium is a medicine commonly used to treat bipolar disorder and may be prescribed for individuals who have depression that does not respond adequately to other treatments. This test helps doctors determine whether the lithium level in the blood is within the recommended range for safe and effective treatment.

Lithium has a narrow therapeutic range, meaning the amount needed for effective treatment is close to the amount that may cause side effects. Due to this, regular monitoring is important to ensure that the medicine remains both safe and effective. Doctors may order this test when a person starts lithium therapy, after a dose adjustment, during routine follow-up visits, or when there is a concern that lithium levels may be outside the target range. Blood samples are typically collected about 12 hours after the last dose.

The lithium test primarily monitors how the body responds to lithium treatment and helps guide dosage adjustments. It also plays an important role in helping monitor the kidneys, which remove lithium from the body, as changes in kidney function can affect lithium levels. In addition, healthcare providers may monitor the thyroid gland because long-term lithium therapy can sometimes affect thyroid function. Regular testing of lithium levels may help support the safe and effective long-term use of lithium.

A doctor may advise a lithium blood test for people who may be experiencing symptoms that could suggest high levels of lithium, such as:

• Nausea or vomiting
• Diarrhoea or stomach pain
• Dizziness
• Muscle weakness
• Tremors or shaking of the hands
• Poor coordination or difficulty walking
• Slurred speech
• Confusion or changes in mental state
• Increased thirst or changes in urination
• Seizures

Some people may also require this test because they need closer monitoring while receiving lithium treatment. These include:

• People who are starting lithium treatment or have recently had their dose changed
• People taking medicines that can affect lithium levels
• Adults aged 65 years and older
• People with kidney disease or reduced kidney function
• People with thyroid disorders or those at risk of thyroid problems
• Pregnant women taking lithium
• People with significant changes in fluid or salt levels, due to conditions such as excessive sweating, vomiting, or diarrhoea
• People whose symptoms are not adequately controlled with lithium treatment

The frequency of lithium testing depends on whether treatment has just started, the dose has changed, or lithium levels are already stable.

A lithium test is primarily used to monitor lithium therapy and identify lithium-related problems, including:

• Lithium toxicity: High lithium levels can lead to symptoms such as nausea, vomiting, diarrhoea, tremors, dizziness, confusion, slurred speech, poor coordination, seizures, and, in severe cases, coma.
• Subtherapeutic (lower than needed for effective treatment) lithium levels: Low lithium levels may indicate that the medication is not present in sufficient amounts to effectively manage bipolar disorder or other conditions being treated with lithium.
• Kidney function problems related to lithium therapy: Long-term lithium use may affect kidney function and monitoring helps identify possible kidney-related complications.
• Thyroid problems associated with lithium use: Lithium treatment may contribute to thyroid dysfunction and regular monitoring is often recommended.
• Treatment monitoring in bipolar disorder: The test helps ensure that lithium levels remain within the therapeutic range so that treatment remains effective while minimising the risk of side effects and toxicity.

What to Expect Before the Lithium Test

No fasting is required for a standalone Lithium test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise Lithium levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the Lithium Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

This test measures one important parameter:

• Lithium level in the blood to check whether the level is within the range needed for safe and effective treatment.

The lithium test measures the level of lithium in the blood and is reported in millimoles per litre (mmol/L). The lithium normal range is given in the table below:

The lithium test result is interpreted by comparing the lithium level in your blood with the recommended reference range, as shown in the table below:

Note: Dehydration, changes in salt intake, kidney problems, and certain medicines can affect lithium levels. Regular testing helps ensure that treatment remains safe and effective.

The lithium test is a simple and safe blood test. However, like most blood tests, it has some minor risks and limitations.

Possible Risks of the Test

Some people may experience mild pain, slight bleeding, or a small bruise at the blood sample collection site. These effects are usually temporary and resolve on their own within a short time.

Limitations of the Lithium Test

• Certain medications, supplements, and over-the-counter drugs may increase, decrease, or interfere with lithium concentrations, which can affect test results.
• Conditions that cause loss of salt and water from the body, such as excessive sweating, vomiting, diarrhoea, or a low-sodium diet, may increase lithium levels and influence the test result.
• People with kidney disease may have higher lithium levels because lithium is removed from the body primarily through the kidneys.
• The test result should be interpreted along with a person's symptoms, medical history, and other laboratory findings.

Doctors may advise the following tests along with the lithium test to monitor treatment and check for possible side effects:

• Thyroid function tests (TSH and/or free T4)
• Kidney function tests, such as urea and creatinine tests
• Estimated glomerular filtration rate (eGFR)
• Urea and electrolyte (U&E) tests
• Serum calcium test
• Complete blood count (CBC)
• Electrocardiogram (ECG), especially for people with cardiovascular disease or risk factors
• Repeat lithium level tests for dose adjustment and routine monitoring