If you’ve been diagnosed with high cholesterol in winter, you may want to get retested in the summer. Blood cholesterol levels peak in fall and winter but drop during spring and summer, according to a study published in the Archives of Internal Medicine (2004, vol. 164, no. 8).

The study included 517 participants, ages 20 to 70, whose blood cholesterol levels were checked every three months for a year. Average levels increased by 3.9 mg per deciliter (dL) of blood in men, with a peak in December, and increased 5.4 mg/dL in women, with a peak in January. Variations of up to 18 points were found in participants with initial cholesterol levels above 240.

Researchers say changes in physical activity, light exposure, temperature, and blood volume contribute to this phenomenon. “More people are diagnosed with high cholesterol during the winter months,” says study author Edward J. Stanek, PhD, professor of biostatistics and chair of biostatistics and epidemiology at the University of Massachusetts, Amherst. “Physicians and patients should be aware that cholesterol levels vary over the seasons. If you’re concerned about a diagnosis that was made in the winter, speak to your physician.”

Total Cholesterol Level


Less than 200 mg/dL


200–239 mg/dL

Borderline High

240 mg/dL and above