The Pharmacy Channel is a nationwide media service available in 1,000 UK chemists. It originated in the US before coming to the UK two years ago and is available only to independent pharmacies, not chains such as Boots.
It has more than doubled its output since starting as a London-wide service showing at 400 pharmacies.
The channel will animate print adverts free of charge and offers discounts to charities for the cost of screening the finished product.
The channel estimates that about 4.8 million people will see the service in their local pharmacy over a two-month period.
Fraser Sim, sales and marketing manager of the Pharmacy Channel, says: "The Diabetes UK campaign is designed to encourage customers with diabetes to contact the charity for advice and also to educate staff.
"People who go to the pharmacy are in a certain frame of mind, and people with diabetes go more often than those without."
The campaign is part of the charity's drive to use new media to reach its target audience. Mike Hillder, marketing and membership manager of Diabetes UK, explains: "We have been targeting doctors' surgeries and clinics more, and pharmacies are another natural outlet for us. It's easy to calculate how many people you will reach with a press campaign because you can just look at the readership.
But as this is a relatively new service, we are trialling it. If it works, we will think about using it for longer campaigns."
Asthma UK also used the Pharmacy Channel for a month-long campaign in the run-up to and immediately after World Asthma Day on 4 May.
Rachel Williams, assistant director of individual giving at Asthma UK, says: "There were two strands to our awareness-raising push. The first focused on what asthma is and the second looked at what we do.
"It was a positive step for us to use a different environment to get our message across and allowed us to target people picking up their prescriptions."