You should consult your doctor if you experience any of these: • A fall in the number of white blood cells (the cells that fight infection), platelets (the cells that help the blood to clot, which may lead to bleeding disorders) and red blood cells (anaemia leading to tiredness and weakness) • Constipation, diarrhoea, nausea, increase and decrease in weight, rash, sleep disturbance, muscle cramps and muscle weakness, tiredness, swelling of the peripheries.