Low Body Temp After COVID: Potential Causes and Recovery

Some individuals recovering from COVID-19 report experiencing lower-than-normal body temperatures. While fever is a well-documented symptom of viral infections, a drop in temperature post-recovery raises questions about its causes and health implications.

Understanding this phenomenon sheds light on how the body responds to infection and recovers over time.

Regulation Of Body Temperature After Viral Infections

The body maintains a stable internal temperature through a complex system controlled by the hypothalamus, which processes signals from thermoreceptors to regulate heat production and dissipation. Viral infections disrupt this balance, typically causing fever. After recovery, temperature regulation may take time to normalize, leading to fluctuations, including lower-than-normal readings.

Post-viral changes in metabolism can contribute to this. Fever increases energy expenditure, but after recovery, metabolic processes may slow down. Studies on influenza and other infections have shown that reduced metabolic rates post-illness can result in lower core temperatures, particularly in cases of post-viral fatigue.

Circulatory shifts also influence post-infection temperature regulation. Fever triggers vasodilation to release heat, but once it subsides, vasoconstriction may follow, reducing heat distribution to the skin. This can lead to sensations of cold and lower peripheral temperatures. Similar effects have been observed in post-viral dysautonomia, where autonomic imbalances disrupt temperature control.

Possible Mechanisms Leading To Low Body Temperature

Autonomic nervous system dysfunction is a key factor. This system regulates involuntary functions, including thermoregulation. Post-viral dysautonomia, documented in COVID-19 recovery, can impair temperature stability by reducing sympathetic tone, slowing metabolism, and affecting blood vessel responses. This may explain prolonged episodes of low body temperature, especially when accompanied by dizziness, fatigue, and abnormal sweating.

Mitochondrial impairment is another potential cause. Mitochondria generate heat as a byproduct of energy production, but viral infections, including SARS-CoV-2, can cause mitochondrial stress, reducing efficiency. Research in Nature Communications has shown that post-viral mitochondrial dysfunction can persist, affecting metabolism and thermogenesis. This has been linked to post-viral fatigue syndromes, where metabolic inefficiencies contribute to cold intolerance.

Hormonal fluctuations may also play a role. The hypothalamic-pituitary-adrenal (HPA) axis, responsible for stress response, can become dysregulated after viral infections, altering cortisol secretion. Cortisol influences metabolism, and disruptions in its rhythm can reduce energy expenditure and heat production. A study in The Journal of Clinical Endocrinology & Metabolism found that post-viral endocrine imbalances, including transient adrenal insufficiency, may contribute to lower body temperatures. Additionally, post-COVID thyroid dysfunction, such as transient hypothyroidism, has been observed, which can suppress metabolic rate and temperature regulation.

Relationship Between Low Temperature And Immune Responses

The immune system plays a role in post-recovery temperature changes. Fever is a sign of immune activation, but a drop in temperature may reflect lingering immunomodulatory effects. Cytokines, which regulate immune responses, interact with the hypothalamus to influence temperature. During infection, pro-inflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) stimulate fever. As inflammation subsides, anti-inflammatory cytokines such as interleukin-10 (IL-10) may suppress metabolic activity, leading to reduced heat generation.

Immune cell metabolism also affects thermoregulation. During infection, immune cells consume large amounts of energy, generating heat. Once the immune response slows, energy expenditure declines, which may result in lower body temperatures. Studies on post-COVID recovery indicate persistent changes in glucose metabolism and mitochondrial efficiency in immune cells, potentially contributing to temperature fluctuations.

A lower body temperature may also be an adaptive response to prevent excessive inflammation. The resolution phase of the immune response involves regulatory T cells and lipid mediators like resolvins, which restore balance. These mechanisms influence autonomic and metabolic pathways that regulate heat production. Some researchers suggest that post-infection temperature reductions conserve energy while the body repairs damage, a pattern seen in other post-viral syndromes.

Neuroendocrine Factors Affecting Temperature Post Infection

The hypothalamic-pituitary axis is central to temperature regulation, and disruptions after COVID-19 may contribute to prolonged thermoregulatory imbalances. The hypothalamus relies on neurotransmitters and hormonal feedback loops to control heat production and dissipation. Studies on post-viral syndromes suggest that neuroendocrine dysfunction can persist after infection, affecting metabolism and thermogenic responses.

Thyroid function is particularly influential. Thyroid hormones, especially triiodothyronine (T3) and thyroxine (T4), regulate metabolism and heat production. COVID-19 has been linked to temporary thyroid dysfunction, including low T3 syndrome and post-viral thyroiditis, both of which can suppress metabolic activity and lower body temperature. Research in The Journal of Clinical Endocrinology & Metabolism has documented cases of altered thyroid hormone levels in COVID-19 recovery, contributing to fatigue, cold intolerance, and sluggish thermoregulation.

Post COVID Lifestyle Factors Affecting Thermoregulation

Lifestyle habits also impact post-COVID temperature regulation. Changes in physical activity, sleep patterns, and nutrition can influence recovery. Many individuals experience reduced physical exertion due to lingering fatigue, which lowers metabolic heat production. Exercise stimulates thermogenesis by increasing muscle activity and circulation, so a lack of movement can contribute to cold sensations. Gradually reintroducing activity, such as light stretching or low-intensity exercise, may help restore normal temperature regulation.

Sleep disturbances further affect thermoregulation. The body’s circadian rhythm naturally causes temperature fluctuations, with a dip during sleep. However, post-viral insomnia or irregular sleep cycles can disrupt this pattern, prolonging periods of reduced body temperature. Research in Sleep Medicine Reviews indicates that disrupted sleep can impair thermoregulatory responses by altering melatonin secretion, which influences vascular control and metabolism. Maintaining consistent sleep habits and reducing screen exposure before bedtime can support temperature stabilization.

Nutritional intake also plays a role. Inadequate calorie consumption slows metabolism, affecting heat production. Ensuring sufficient intake of protein, healthy fats, and micronutrients like iron and B vitamins can aid in restoring normal metabolic function and thermoregulation.

Indicators For Medical Evaluation

Mild temperature fluctuations during post-COVID recovery are usually temporary, but persistent or severe reductions may indicate underlying issues. Consistently low body temperatures below 95°F (35°C), especially when accompanied by dizziness, cognitive impairment, or unusual fatigue, warrant medical evaluation. Clinicians may conduct thyroid function tests, cortisol level assessments, and autonomic nervous system evaluations to identify potential causes.

Temperature dysregulation may also be linked to long COVID. Some individuals with persistent symptoms report abnormal thermoregulatory responses alongside cardiovascular, neurological, and metabolic dysfunction. A study in The Lancet found that autonomic instability in long COVID patients can lead to irregular temperature control, reinforcing the need for thorough assessment. If low body temperature is accompanied by unexplained weight loss, persistent bradycardia, or difficulty maintaining homeostasis in different environments, further diagnostic testing may be necessary. Early intervention can guide appropriate treatment, whether through lifestyle adjustments, medical management, or rehabilitative therapies aimed at restoring normal temperature regulation.