Reduced male libido may be linked to low levels of the male hormone testosterone, while a drop in sex drive in women can be triggered by anaemia, when lack of red blood cells cause iron deficiency.
Iron is crucial for transporting oxygen around the body, so anaemia triggers excess tiredness, which can lead to a lack of sex drive. The condition can be detected through a blood test and treated with iron supplements.
Less commonly, low libido may be caused by an underactive thyroid. Failure of the thyroid gland to produce enough thyroxine hormone, needed for energy, can lead to lethargy and a lack of interest in sex. The condition can be treated with thyroid hormone-replacement drugs.