Low blood sugar levels are common in babies after birth. This may be normal as babies can use other sources of energy. However if a baby does not produce these fuels the brain can be starved of energy and be damaged. Measurement of these fuels is not done as part of clinical practice in the newborn. We aim to see whether at the same time as taking the blood sugar level from a heel prick we can measure these fuels in a small drop of blood. At the same time as blood needs to be taken for clinical reasons we want to take a drop of blood from 50 babies to see how good the point of care (POC) meters are compared to the laboratory at measuring these fuels. If accurate these POC meters could identifying those at risk from brain damage as well as prevent separation of mothers and babies who are establishing breast feeding.