Some psychiatric medications need regular blood tests and many do not. Lithium, valproate, carbamazepine and clozapine are the clearest examples of medications that call for blood work. Newer antipsychotics usually call for checks of blood sugar and cholesterol. Most SSRIs, SNRIs and ADHD stimulants do not have a routine blood-test schedule on the labels reviewed here, though blood pressure, weight or targeted tests may still matter.
Part of our guide: A Patient’s Guide to Psychiatric Medication
What applies to you depends on your medication, your age, your health and your other prescriptions. Your prescriber decides what to order and how often. The table below explains what FDA labels say, so you can ask informed questions. Which tests Mind Body Seven orders, and how, is something to ask the intake team or your clinician.
If you are thinking about suicide or are in crisis: call or text 988 (988 Suicide & Crisis Lifeline), call 911 or go to the nearest ER.
Quick reference from FDA labels
| Medication | Tests the label describes | Why |
|---|---|---|
| Lithium | Lithium blood levels; kidney function; electrolytes; thyroid; calcium | Toxic levels sit close to the treatment range; long-term kidney, thyroid and calcium effects |
| Valproate (divalproex) | Liver tests; blood counts including platelets; clotting tests; valproate levels; ammonia if symptoms appear | Liver failure, bleeding and blood count problems, high ammonia |
| Carbamazepine | HLA-B*1502 genetic test for at-risk ancestry; blood counts; liver tests; kidney checks; drug levels; sodium if symptoms | Severe skin reactions, bone marrow suppression, liver damage, low sodium |
| Clozapine | Absolute neutrophil count (ANC) at baseline and regularly | Severe neutropenia, which raises the risk of serious infection |
| Quetiapine and other atypicals | Glucose; fasting lipids; with quetiapine, thyroid tests, and a blood count in people with a low white cell history | Metabolic changes, thyroid effects, low white cell counts |
| Lamotrigine | No routine schedule in the sections reviewed; the boxed warning concerns rash | Blood problems are reported, so report new symptoms. Call right away about any rash |
| SSRIs and SNRIs | No routine schedule on the labels reviewed; sodium if symptoms; blood pressure for venlafaxine; INR if taking warfarin; potassium and magnesium for at-risk people on citalopram | Low sodium, higher blood pressure, bleeding risk |
| Stimulants | No routine blood tests on the label reviewed; blood pressure, pulse and growth instead | Heart rate, blood pressure, growth in children |
| Atomoxetine | Liver tests at the first sign of liver problems | Rare severe liver injury |
Lithium
Lithium has the most established monitoring. Its boxed warning says toxicity is closely related to blood levels and can occur at doses close to treatment levels. Before starting, the label calls for checking kidney function, vital signs, electrolytes and thyroid function, along with other medications and pregnancy status. Over time, it also advises monitoring thyroid function (before starting, at three months and every six to twelve months) and checking calcium regularly. NIMH likewise describes regular checks of lithium levels and kidney and thyroid function.
Timing matters. The label says blood for a lithium level should be drawn immediately before the next dose, about 12 hours after the previous one. Ask your clinician exactly how to time your blood draw.
Several things can raise lithium levels, including diuretics, NSAIDs and some blood pressure medicines. Check before starting any new medicine, including over-the-counter pain relievers. The label says toxicity risk also rises with a new illness with fever, dehydration or kidney problems, so ask what to do if you get sick. It also says not to double a dose after missing one. The label lists signs of toxicity such as diarrhea, vomiting, tremor, lack of coordination, drowsiness, abnormal heart rhythm or muscle weakness. The label tells patients who notice these signs to stop lithium treatment and contact their health care provider. Treat this as urgent and call your prescriber right away, before your next dose. If you cannot reach anyone promptly, or symptoms are severe, call 911 or go to the nearest ER.
Valproate and carbamazepine
Valproate's boxed warning says serum liver tests should be performed before therapy and at frequent intervals afterward, especially during the first six months. The label also calls for monitoring platelet counts and coagulation tests, and for measuring ammonia if someone develops unexplained lethargy, vomiting or changes in mental status. The boxed warning also covers life-threatening pancreatitis, so abdominal pain, nausea, vomiting or loss of appetite need prompt medical evaluation.
There is also an important pregnancy warning. Valproate can cause major birth defects and decreased IQ after exposure in pregnancy. It should not be used in people with bipolar disorder who are pregnant or planning pregnancy unless other medications have failed or are otherwise unacceptable. If pregnancy is possible, talk with your prescriber early and ask about reproductive psychiatry. If you are or might be pregnant, call right away rather than stopping on your own.
Carbamazepine's boxed warning says patients with ancestry in at-risk populations should be screened for HLA-B*1502 before starting, because of the risk of severe skin reactions. It also recommends baseline blood counts and baseline and periodic liver function evaluations. This is one case where a genetic test is specifically named on a label. For broader testing, see reasons to consider genetic testing and discuss what it can and cannot show.
Clozapine
Clozapine is labeled for severely ill people with schizophrenia who have not responded adequately to standard treatment, and for lowering the risk of recurrent suicidal behavior in schizophrenia or schizoaffective disorder. It calls for a baseline ANC and regular monitoring throughout treatment. FDA has determined that its REMS program is no longer necessary, but it still recommends monitoring ANC at the frequencies in the prescribing information, and the risk remains in the boxed warning. Follow your care team's testing schedule.
Newer antipsychotics
The quetiapine label advises monitoring glucose regularly in people with or at risk of diabetes, fasting blood lipid testing at the start and periodically, and clinical monitoring of weight. It also advises measuring both TSH and free T4 at baseline and follow-up and checking blood counts in people with low white cell history. Report increased thirst, increased urination, increased appetite or weakness. See why antipsychotics are prescribed for mood disorders for more on these medicines.
SSRIs, SNRIs and stimulants
Sodium is the main blood test to know about with SSRIs and SNRIs. Older adults, people on diuretics and people who are volume depleted may be at greater risk of low sodium. Headache, trouble concentrating, confusion, weakness or unsteadiness should prompt a call. If you take warfarin, the sertraline label says to carefully monitor the INR. The citalopram label adds baseline potassium and magnesium tests with periodic monitoring for people at risk of electrolyte problems. The venlafaxine label reports increases in serum cholesterol in studies, so ask whether checking yours makes sense for you.
With stimulants, the Concerta label focuses on blood pressure, heart rate and growth in children rather than a set schedule of lab work. How often you see your provider can depend on the medication too.
How often will you need tests?
Labels often describe what to monitor without giving one schedule for everyone, and the right timing depends on how long you have been taking the medication, recent changes, your age and your other conditions. More frequent checks are common around the start of treatment and after changes. Ask your clinician to tell you what is due, and when, and keep your own simple record of test dates so nothing slips through a change of pharmacy, insurer or clinician.
How to prepare for your labs
- Ask what is being ordered and why. Knowing what the test is for makes the results easier to discuss.
- Ask whether to fast, what to do about your dose that morning, and when to have blood drawn.
- Share recent results. Your primary care clinician may already have checked some of these. Bring copies so tests are not repeated.
- Bring an updated medication list, including supplements and over-the-counter medicines. These can affect results and interact with prescriptions.
- Ask who follows up, when you can expect results and what happens if something is out of range.
- Check costs. Lab coverage depends on your insurance plan and the lab, so ask your plan before your test.
A result outside the usual range does not automatically mean you need to stop your medication, and only your prescriber can interpret it in context. If you get a result that worries you, call the office and ask what to do. Make any change only with your prescriber. If you have severe symptoms, seek urgent care.
Where to go from here
If you take any of these medications and are unsure what monitoring you need, medication management is the right place to ask. For questions about costs, see fees and insurance.
FAQs
Are blood tests needed before starting an antidepressant?
The SSRI and SNRI labels reviewed here do not set a routine blood-test schedule, but your clinician may still want tests based on your health or symptoms. Fatigue and low mood can have medical causes, so ask whether any workup makes sense for you.
Can a local lab or primary care doctor do the tests?
Often it is possible, but it depends on your plan and your clinician. Ask your clinician where results should go and ask your insurer which labs are covered. Share any recent results so tests are not repeated unnecessarily.
Can a blood test show which psychiatric medication will work?
No routine blood test can reliably predict that for most people. Levels can help for some medications, such as lithium, and a genetic test is named on the carbamazepine label for safety. Ask your clinician what any test can and cannot tell you.
