Why does your psychiatrist ask for blood tests?

You arrive for a medication follow-up expecting questions about sleep and mood. Instead, someone hands you a laboratory order featuring several abbreviations and the conversational warmth of a parking citation. You nod, put it in your bag, and later wonder whether your psychiatrist suspects your kidneys are staging a coup.

Blood tests in psychiatric care can answer very different questions. Some look for medical conditions that can resemble or worsen mental health symptoms. Some establish a baseline before treatment. Others check whether a medication is at a useful level or affecting organs, blood cells, glucose, or cholesterol. The order should have a reason. “Psych labs” isn’t a single mysterious package delivered by the same department as your personality.

A test should have a job, not just a checkbox

Psychiatric symptoms live in a body. Thyroid problems can overlap with mood, anxiety, energy, or concentration changes. Anemia, vitamin deficiencies, infection, pregnancy, sleep disorders, substance use, and medication effects can matter in the right context. That doesn’t mean everyone needs every test.

A clinician should choose testing from your symptoms, history, examination, medications, health conditions, pregnancy possibility, and treatment plan. Broad testing can occasionally find something important, but it can also produce borderline results that don’t explain the problem. More ink on the order isn’t automatically more thoughtful medicine.

Ask one clean question: “What are we looking for, and what would the result change?” A useful answer might be, “We’re checking thyroid function because of your new fatigue,” or, “We need kidney and thyroid baselines before lithium.” If nobody can explain the job, the test may need a better conversation.

I’ll also want to know who owns the result. Is the psychiatrist reviewing it, the primary-care clinician, or both? When should you expect a message? What should happen if it’s abnormal? A laboratory portal can release a red number before breakfast. It shouldn’t be left to provide solo interpretive dance.

Some tests create a baseline for comparison

A baseline is a snapshot taken before or near the start of treatment. It helps separate what was already present from what changes later. Depending on the medication, that snapshot may include weight, blood pressure, glucose or hemoglobin A1c, cholesterol and triglycerides, kidney function, liver tests, thyroid function, blood counts, electrolytes, or a pregnancy test when relevant.

Antipsychotic medications can differ in their likelihood of affecting weight, glucose, and lipids, and people differ in their vulnerability. Guidelines recommend physical and metabolic monitoring rather than waiting for symptoms of high blood sugar or cholesterol, which may not announce themselves politely. Weight and blood pressure aren’t blood tests, but they belong to the same safety picture.

An abnormal baseline doesn’t automatically ban a medication. It may change which option is favored, how risks are discussed, what needs treatment, or how often monitoring occurs. The decision should consider expected benefit, alternatives, the condition being treated, personal risk, and your preferences.

Try this today: make a tiny monitoring note with four headings: test, reason, due date, owner. Add only what you’re actually supposed to complete. You don’t need a color-coded command center. You need a plan that survives contact with a normal Tuesday.

Lithium needs levels and organ monitoring

Lithium has strong evidence for some mood conditions, and it requires structured monitoring. Clinicians check a blood level because too little may not help and too much can become toxic. The timing of the draw matters, especially in relation to the last dose, so follow the laboratory and prescriber instructions rather than choosing a convenient random hour.

Before and during lithium treatment, guidelines also call for monitoring kidney and thyroid function and calcium, along with other baseline health checks. Kidneys clear lithium. Thyroid and calcium changes can emerge over time. The schedule becomes more frequent after starting, after dose changes, when levels aren’t stable, or when risk changes.

Dehydration, vomiting, diarrhea, fever, major changes in salt intake, and interacting medications can affect lithium safety. Don’t adjust or stop it from an article. Contact the prescriber promptly for new vomiting, diarrhea, marked tremor, confusion, severe unsteadiness, unusual drowsiness, or another possible toxicity symptom. Severe symptoms need urgent medical care.

Tell every prescriber and pharmacist that you take lithium. An over-the-counter pain reliever or a new blood-pressure medication may look unrelated to mood treatment while still affecting lithium levels. The safest medication list is the one that leaves the notes app and enters the actual conversation.

Other medications have different reasons for testing

Valproate or divalproex may require liver tests and blood counts, along with additional precautions. Pregnancy prevention and reproductive risks require especially careful, current counseling because fetal risk is serious. Monitoring and prescribing rules can change, so the plan must come from the treating clinician and current guidance, not a generic schedule online.

Carbamazepine can affect blood counts, liver function, sodium, and drug interactions. Some people need genetic testing before starting it because certain inherited variants raise the risk of severe skin reactions in specific ancestry groups. Lamotrigine usually isn’t managed by routine blood levels in ordinary care, but any new rash needs prompt guidance because rare serious reactions can occur.

Many antidepressants and ADHD medications don’t require routine blood measurement of the drug itself. Monitoring may still include blood pressure, pulse, weight, sodium in higher-risk situations, or tests suggested by symptoms and health history. “No routine blood level” doesn’t mean “no follow-up.” Response, sleep, mood, side effects, safety, and functioning still count.

Don’t compare your laboratory schedule with a friend’s and assume one of you is receiving better care. Different medications, doses, ages, health conditions, symptoms, and risk factors create different plans. Matching tote bags are lovely. Matching laboratory orders aren’t required.

An abnormal result is a question, not a verdict

Reference ranges aren’t moral grades. A value can be slightly outside a range because of timing, fasting status, hydration, illness, laboratory variation, or a real health issue. Meaning comes from the degree of change, prior results, symptoms, and the test’s purpose.

Ask whether the result needs repeating, primary-care follow-up, a treatment change, or no action. Don’t stop medication abruptly unless a qualified clinician tells you to, except when emergency services direct immediate care. Some psychiatric medications can cause withdrawal symptoms or relapse when stopped suddenly.

If needles are difficult, say so before the draw. You can ask to lie down, use a smaller needle when appropriate, work with an experienced phlebotomist, bring support if allowed, and discuss strategies for fainting or panic. Avoidance can make monitoring less safe, but shame doesn’t make the needle smaller.

Good monitoring isn’t busywork. It’s a way to notice benefit, risk, and physical health early enough to act. You don’t deserve a stack of unexplained orders. Know the purpose, keep the schedule, and make sure someone closes the loop. The blood test is one data point in your care, not an oracle in a plastic chair.

If distress includes thoughts of suicide, you can’t stay safe, or someone is in immediate danger, call or text 988 in the United States; call 911 for immediate danger. A laboratory result can inform care, but it shouldn’t delay urgent help.

Sources: National Institute for Health and Care Excellence, bipolar disorder assessment and management guideline, including lithium and antipsychotic monitoring (updated 2025); National Institute for Health and Care Excellence, depression treatment and monitoring guideline (updated 2022); U.S. Food and Drug Administration, lithium carbonate prescribing information (revised 2023); U.S. Food and Drug Administration, divalproex sodium prescribing information and medication guide (revised 2024).