Blood stock levels have fallen as more people cancel sessions due to illness and an annual drop in summer due to people going on holidays and to events.
The session in Fareham is only 78 per cent full with the Gosport session 54 per cent full.
It comes after hospitals are calling on donors to come forward, particularly those with the O positive and B negative blood type.
A spokesperson for NHS Blood and Transplant said: ‘Hospitals are continuing to receive all the blood they need but more donations are urgently needed to ensure stocks do not fall further.’
Go to www.blood.co.uk to make an appointment for either session or call 0300 123 23 23.