Current Diabetes UK guidelines on self-monitored blood testing say hands should always be washed, but the charity said it may revise its advice on the basis of the findings.
The findings could reduce the risk of diabetes patients missing tests if they are unable to wash their hands.
Diabetes UK's clinical adviser Cathy Moulton said the study demonstrated that the first drop of blood is acceptable if hands have been washed.
'Should it not be possible to hand wash, then the second drop of blood would be the cleaner alternative, after having wiped away the first,' she said.
'We will look into this study in detail and may well use this as evidence to update our current guidelines,' she added.
Dr Henk Bilo and colleagues from Isala Clinics in Zwolle studied the reliability of blood glucose finger-prick testing in 123 people with diabetes.
Even though millions of people with diabetes test their blood glucose everyday, few studies have looked at how best to obtain accurate results.
The researchers said that, although washing hands before tests remained the best option, this was not always possible.
'The first choice is to wash hands with soap and water, dry them, and use the first drop of blood for self-monitoring blood glucose,' they said.
'If washing hands is not possible, and they are not visibly soiled or exposed to a sugar-containing product, it is acceptable to use the second drop of blood after wiping away the first.'
The study found firmly squeezing fingers to obtain blood could affect test results and should be avoided.
RCGP clinical lead for diabetes Dr Brian Karet said patients should be aware that food and dirt on hands can affect results. Patients should be wary of meter results that seem to disagree with how they feel and repeat tests, he said.
'Lots of people don't test at all,' he added. He said it was important not to discourage diabetes patients from testing.