Differential Diagnosis for Chills without Fever

• Single most likely diagnosis
  • Viral upper respiratory infection: This is a common condition that can cause chills without fever, often accompanied by other symptoms such as cough, sore throat, and runny nose. The absence of fever does not rule out a viral infection, as not all viral infections present with fever.
• Other Likely diagnoses
  • Allergic reactions: Allergic reactions can cause chills, especially if they involve anaphylaxis or a significant histamine release. While fever is not typically a primary symptom, chills can occur due to the body's immune response.
  • Anxiety or panic attacks: Severe anxiety or panic attacks can lead to physical symptoms including chills, without the presence of fever. The body's stress response can manifest in various ways, including chills.
  • Hypothyroidism: In some cases, hypothyroidism can cause feelings of coldness or chills, even in the absence of fever. This is due to the decreased metabolic rate associated with thyroid hormone deficiency.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Sepsis without fever (in immunocompromised patients): Although sepsis typically presents with fever, some patients, especially those who are immunocompromised, may not develop a fever. It's crucial to consider sepsis in the differential diagnosis, even without fever, as it is a life-threatening condition.
  • Malignant hypothermia: This is a rare but life-threatening medical emergency that can occur in response to certain anesthetics. It presents with muscle rigidity, fever, and other symptoms, but in early stages, patients might experience chills without fever.
  • Adrenal insufficiency: This condition, where the adrenal glands do not produce adequate amounts of hormones, can lead to a variety of symptoms including chills. It's a critical diagnosis not to miss, as adrenal crisis can be fatal.
• Rare diagnoses
  • Relapsing fever (caused by Borrelia species): This infection is characterized by recurring episodes of fever, but between these episodes, patients might experience chills without fever.
  • Brucellosis: A zoonotic infection that can cause undulant fever, where the patient experiences periods of normal temperature interspersed with fever and chills.
  • Drug-induced chills: Certain medications can cause chills as a side effect, without necessarily inducing fever. This can be seen with drugs that affect the immune system or cause vasodilation.