Aching muscles all over can occur with the early stages of a viral infection even before a fever appears, or as it resolves. Common non-infectious causes include physical overexertion, poor or insufficient sleep, stress and tension, dehydration, and vitamin D deficiency. Some medicines, including certain cholesterol-lowering drugs, can also cause muscle aches.
Longer-lasting or unexplained body-wide pain can relate to conditions such as fibromyalgia, thyroid problems, or autoimmune disease, and is worth investigating if it persists for weeks, disturbs sleep, or comes with fatigue, stiffness, or swelling.
Seek prompt care if body aches come with a high fever and stiff neck, a spreading rash, severe muscle pain with dark urine, or significant weakness. Otherwise, rest, fluids, gentle movement, and a pharmacist's advice on pain relief usually help. If aches do not settle, see a doctor. Informational only.