Lab Work in Bipolar Care

People often ask whether a blood test can show bipolar disorder. It cannot: NIMH is clear that no blood test or brain scan can diagnose it. Lab work still plays two important roles. At the start, it helps rule out medical problems and substances that can cause mood symptoms, such as an overactive thyroid. Once treatment begins, it keeps medications safe, because several bipolar medications affect the kidneys, thyroid, liver, blood cells or metabolism. This guide explains both, medication by medication, without target numbers, which are for your prescriber to interpret.

Can a blood test detect bipolar disorder?

No. Bipolar disorder is diagnosed from your history, symptoms and course over time, ideally with input from people who know you. NIMH states that no blood test or brain scan can diagnose it, and that tests may be used to rule out other causes. Genetic tests cannot diagnose it either; see pharmacogenomic testing in bipolar disorder. For how the diagnosis is actually made, read how bipolar disorder is diagnosed.

Rule-out tests at the first evaluation

NIMH notes that thyroid disease and some prescribed, recreational or illicit drugs can mimic or worsen mood symptoms. NICE lists hypo- and hyperthyroidism, drug misuse and alcohol use disorders among the conditions to consider. Depending on your history, a first workup may include:

Brain imaging is not a routine part of the workup. It is considered when the history or a neurological exam suggests another cause. A normal result on any of these tests does not confirm or rule out bipolar disorder; it narrows the list of other explanations.

Bipolar disorder and the thyroid

The thyroid comes up twice in bipolar care. Before diagnosis, thyroid problems are a mimic to rule out. During treatment, lithium can cause both underactive and overactive thyroid, so thyroid function is checked before lithium starts and regularly after; NICE also advises more frequent testing if mood symptoms might be thyroid-related. Standard thyroid tests (TSH and free T4, with antibodies when there is a reason) answer these questions. Reverse T3 is not used to diagnose or monitor bipolar disorder.

Safety labs by medication class

Medication labs follow each drug's FDA label and guideline advice. This is an overview; our guide to which lab tests psychiatric medications need covers each one in full, and your prescriber sets your schedule.

Lithium

Before starting, the label lists kidney function, vital signs, electrolytes, thyroid function, a medication review and pregnancy status; NICE adds weight or BMI, calcium and a full blood count. During treatment, lithium blood levels are checked regularly, along with kidney function, thyroid and calcium, because long-term lithium can affect all three. Levels are timed to the last dose, and illness, dehydration and some common medicines (NSAIDs, diuretics, ACE inhibitors and ARBs) can raise them. Our page on lithium levels explains what a lithium result means.

Valproate (divalproex)

The boxed warning covers liver injury, usually in the first six months, as well as pancreatitis and fetal risk, so liver tests are done before and during treatment, and platelets are watched. Valproate is contraindicated in people with POLG mitochondrial disorders, and pregnancy planning is part of monitoring for anyone who could become pregnant.

Carbamazepine

A blood count before starting and periodically after, because of rare aplastic anemia and agranulocytosis, plus HLA-B*15:02 testing before starting in people likely to carry it.

Lamotrigine

Lamotrigine's main safety issue, serious rash, is watched clinically rather than with routine blood tests. HLA-B*15:02 has been listed on its boxed warning since October 2025. Estrogen-containing contraceptives and pregnancy can lower lamotrigine levels, which your prescriber takes into account.

Atypical antipsychotics

NICE lists weight or BMI, pulse, blood pressure, fasting glucose or HbA1c and lipids before starting, with an ECG if the product information requires it or heart risk factors are present, then repeat checks over the first months. Clozapine also requires ongoing neutrophil counts; its REMS program ended in June 2025, but the monitoring did not. See bipolar medications and weight gain for the metabolic side.

The yearly physical health check

NICE recommends that everyone with bipolar disorder have a physical health check at least once a year, covering weight or BMI, diet, activity, blood pressure, glucose or HbA1c and lipids. People on long-term lithium also need kidney function, thyroid function and calcium. This matters because bipolar disorder is linked with higher cardiovascular risk. Sharing results between your psychiatric prescriber and primary care clinician avoids duplicate draws.

Advanced lab testing: where it fits

Willow & Stone offers advanced psychiatric lab testing for people whose history calls for a broader look, for example at nutrients, hormones or metabolic health. In bipolar disorder, these results can help explain contributors such as fatigue, sleep problems or medical conditions that affect mood, and they can be drawn alongside medication safety labs. They do not diagnose bipolar disorder, they do not replace mood stabilizers, and results are read against standard reference ranges and in the context of your symptoms.

What lab results can and cannot tell you

A lab result is a snapshot. A normal thyroid test makes a thyroid cause unlikely but says nothing about whether bipolar disorder is present. A lithium level reflects the last few days of doses, fluids and illness, not just the prescription. Liver tests on valproate or blood counts on carbamazepine are checks for rare harms, so a normal result is reassuring rather than a sign the drug is working.

Results inside the reference range are generally reassuring, and results outside it are interpreted alongside your symptoms and other medicines rather than in isolation. If a result is flagged, ask what it means for you, whether it needs repeating, and whether it changes the plan. Avoid changing a dose or stopping a medication because of a number you saw in a portal before your prescriber has reviewed it.

Making lab work easier

• Keep a simple record of lab dates and results, or ask for copies through your patient portal.
• Ask when to time a lithium or valproate blood draw relative to your last dose.
• Tell your prescriber about new prescriptions from other clinicians, especially blood pressure medicines, diuretics, pain relievers and antibiotics.
• Labs are billed by the outside lab; ask about coverage before the draw if cost is a concern.

At Willow & Stone

At Willow & Stone, labs are ordered as needed, both to rule out other causes at the evaluation and to keep medications safe over time. Read about bipolar disorder treatment at Willow & Stone, return to the bipolar disorder guide, or book a consultation.

Common Questions

Sources & Further Reading

• NIMH: Bipolar Disorder in Children and Teens (NIH Pub. 23-MH-8081, 2023)
• NIMH: Bipolar Disorder (NIH Pub. 25-MH-8088, 2025)
• NICE CG185: Bipolar disorder: assessment and management (last updated 2 Sept 2025)
• Merck Manual Professional: Bipolar Disorders (2026)
• Merck Manual Professional: Depressive Disorders
• DailyMed: Lithium carbonate prescribing information (4/2026)
• DailyMed: Depakote (divalproex) prescribing information (3/2026)
• FDA Drug Safety Communication: FDA removes REMS program for clozapine (Aug 2025)

This article is general education, not a diagnosis or advice for your situation. Do not start, stop, or change a medication without talking to the clinician who prescribes it; stopping a mood stabilizer suddenly can trigger relapse.