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Nortriptyline Test

The nortriptyline test monitors blood levels of this tricyclic antidepressant, as prescribed by your doctor. As part of comprehensive health monitoring, this test helps your healthcare provider ensure your medication levels support optimal treatment outcomes.

Doctor's Assessment Included

When is this value abnormal?

Decision limits per result, in ug/l
Result Value (ug/l)
Subtherapeutic < 70
Therapeutic 70–170
Above therapeutic range ≥ 170

Trough level (drawn before the next dose). Toxic: > 300 µg/l.

Source: UMC Utrecht

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Nortriptyline: what this test measures

This test measures the blood concentration of the tricyclic antidepressant nortriptyline, as prescribed by your doctor. Monitoring supports your healthcare provider in optimizing your treatment.

Nortriptyline: why this value matters

Nortriptyline has a well-defined therapeutic range. Levels below this range may not provide adequate symptom relief, while levels above it can be associated with an increased risk of side effects or toxicity, including cardiac effects.

Nortriptyline: how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
on its own €49,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Nortriptyline: when is testing worthwhile?

Testing is typically recommended when starting nortriptyline therapy, after dose adjustments, when adding interacting medications, or when symptoms suggest subtherapeutic or excessive levels. Your healthcare provider will advise on the appropriate schedule.

Nortriptyline: symptoms of a high or low value

Low Levels

Low nortriptyline levels may indicate subtherapeutic dosing, which can be associated with persistent depressive symptoms or inadequate pain relief. Consult your healthcare professional for interpretation of results.

High Levels

High nortriptyline levels may indicate a risk of side effects or toxicity, which can be associated with dry mouth, dizziness, constipation, urinary retention, and in serious cases, cardiac arrhythmias. Contact your healthcare provider if you experience these symptoms.

Nortriptyline: lifestyle and this value

Take nortriptyline exactly as prescribed by your doctor and do not stop or adjust the dose without medical guidance. Keep all scheduled blood monitoring appointments and report any new side effects to your healthcare provider promptly.

Nortriptyline: frequently asked questions

Why is blood level monitoring needed for nortriptyline?

Nortriptyline has a therapeutic window where the medication is most effective. Blood monitoring helps your doctor ensure your levels are within this range, optimizing benefit while minimizing side effects.

Can nortriptyline interact with other medications?

Yes, several medications can affect nortriptyline levels, including certain SSRIs, antipsychotics, and some heart medications. Always inform your healthcare provider about all medications and supplements you are taking.

How long does it take for nortriptyline levels to stabilize?

Nortriptyline levels typically reach a steady state within one to two weeks of consistent dosing. Your doctor may schedule a blood test after this period to check your levels.

Nortriptyline: sources

  1. UMC Utrecht, Divisie Laboratoria en Apotheek. Bepalingenwijzer: therapeutische geneesmiddelspiegels (amitriptyline, nortriptyline, carbamazepine, valproïnezuur, fenytoïne, digoxine, lamotrigine). Geraadpleegd 14 juli 2026. (retrieved 2026) umcutrecht.nl

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Medical reviewer

Medical standards

Dr. Naimi oversees the medical standards behind our content and assessments.

Medical policy
CIBG Ministerie van Volksgezondheid,
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Nortriptyline

€49,-