Quick answer
Yes — in two ways. Some physical illnesses directly produce anxiety symptoms (thyroid problems, heart conditions, and others), and being ill or facing a health condition is itself anxiety-provoking. New or unexplained anxiety warrants a medical check to rule out physical causes.
Illness that directly causes anxiety
Certain physical conditions can directly produce anxiety symptoms as part of their effects. Thyroid problems (especially overactive thyroid) are a classic example, causing anxiety, palpitations, and restlessness. Heart conditions, respiratory conditions, hormonal imbalances, certain neurological conditions, low blood sugar, and some other illnesses can generate anxiety or anxiety-like symptoms. Some infections and their effects, and various medications used to treat illnesses, can too. Because these physical causes produce genuine anxiety symptoms, they can be mistaken for a primary anxiety disorder — which is why a medical evaluation is important for new, sudden, or unexplained anxiety, to identify and treat any physical contributor.
The anxiety of being ill
Separately, being ill or facing a health condition is itself a significant source of anxiety. A serious diagnosis, chronic illness, frightening symptoms, medical procedures, uncertainty about prognosis, and the disruption illness causes to life all understandably provoke anxiety and worry. This is a normal response to a genuinely stressful situation — health and mortality are among our deepest concerns. Chronic illness in particular can involve ongoing anxiety about symptoms, flare-ups, and the future. Even recovering from illness can leave heightened anxiety. This kind of illness-related anxiety is about the psychological impact of being unwell, and it's a common and understandable part of the experience of illness.
What to do
Given both pathways, a few things matter. For new, sudden, or unexplained anxiety — especially with physical symptoms — see a doctor to rule out physical causes; identifying a treatable condition (like a thyroid problem) can resolve the anxiety at its source. For anxiety about being ill or facing a health condition, both practical support (good medical care, information, addressing the illness) and emotional support help — and if health-related anxiety becomes overwhelming or persistent, therapy and support are valuable. Note that intense, disproportionate fear of having a serious illness (health anxiety) is its own pattern with specific effective treatment. Whether illness is causing anxiety directly or through worry, support is available on both the medical and psychological fronts.
Why causes matter — and their limits
Understanding what feeds your anxiety helps you make smart changes, but you don't need to find 'the' cause to recover. Modern treatment works on the maintaining loop — how anxiety sustains itself today — which is why therapy helps even when the original trigger is unclear. A professional can help with both.
This article is for general information only and is not medical advice, diagnosis, or treatment. Always consult a qualified health professional about your situation. If you are in crisis, contact your local emergency number or a crisis line immediately.