Mirtazapine Does Not Typically Cause Hypothermia in Standard Clinical Use
Mirtazapine is not recognized as a cause of hypothermia in standard clinical practice, and the FDA drug label does not list hypothermia as a known adverse effect. 1 However, one isolated case report suggests a possible association in neonates exposed in utero, though this remains unconfirmed and is not relevant to typical adult use.
Evidence from FDA Drug Labeling
The official FDA prescribing information for mirtazapine comprehensively lists potential adverse effects, including serious ones such as:
- Serotonin syndrome (which includes hyperthermia, not hypothermia)
- Low white blood cell count
- Seizures
- Hyponatremia
- Cardiac rhythm problems
- Severe skin reactions
Notably absent from this extensive list is any mention of hypothermia 1. In fact, when discussing serotonin syndrome—a serious potential complication—the FDA specifically warns about high body temperature (hyperthermia) as a key symptom, not low temperature 1.
Clinical Guidelines Perspective
Multiple clinical guidelines from prestigious organizations discuss mirtazapine's use across various conditions:
- American Heart Association (2024): Notes mirtazapine is safe in cardiovascular disease patients, with benefits including appetite stimulation and sleep promotion, but makes no mention of hypothermia 2
- NCCN Palliative Care Guidelines (2016): Recommends mirtazapine for refractory insomnia, particularly in patients with depression and anorexia, without any hypothermia warnings 3
- American College of Physicians (2008): Discusses mirtazapine's faster onset of action compared to other antidepressants, with no hypothermia concerns 4
The Single Case Report
One 2008 case report described recurrent hypothermia in premature twins (born at 35 weeks) whose mother took mirtazapine throughout pregnancy 5. The authors speculated this might relate to mirtazapine's effects on serotonin and alpha-2 receptors affecting thermoregulation. However:
- This is a single case report with no confirmatory evidence
- The twins were premature, which itself can cause thermal instability
- No mechanism was definitively established
- This has never been replicated in the literature
- It does not apply to standard adult use of mirtazapine
Context: Other Antipsychotics and Hypothermia
For comparison, certain antipsychotics (risperidone, olanzapine, quetiapine, aripiprazole, haloperidol) have documented cases of causing hypothermia 6, 7, 8. These medications work through different mechanisms than mirtazapine and have established patterns of temperature dysregulation. Mirtazapine does not share this risk profile.
Clinical Bottom Line
When evaluating a patient with hypothermia who is taking mirtazapine, look for other causes first:
- Sepsis or infection
- Endocrine disorders (hypothyroidism, adrenal insufficiency)
- Environmental exposure
- Other medications (particularly antipsychotics)
- Hypoglycemia
- Alcohol or substance use
Mirtazapine should not be considered a likely culprit for hypothermia in clinical practice based on current evidence.