BLOOD stocks dropped to “critically-low levels” last month – prompting the NHS to call on people to donate.

The NHS has renewed its appeal to donors to book and keep appointments in the coming weeks and months as it remains under Amber Alert.

Following an “amazing response from donors” and hospitals temporarily using less blood, the NHS said stock levels have improved since NHS Blood and Transplant triggered Amber Alert for O type blood in July.

“But once demand returns to normal levels, blood stocks could decline once again unless donors fill the thousands of empty slots currently still available at the 25 fixed donor centres in towns and cities across England,” a spokesperson said.

“While donor centres have been more than 90 percent full since Amber was declared, fill rates drop off sharply over the coming weeks.

“Centres are just 40 percent full in the middle of September and this drops to 21 percent by the end of October.

“There are around 80,000 appointments still available to book between now and the end of October. The NHS urgently needs donors to fill these to ensure stock levels are sustainable.”

They said stocks of O negative are at 7.8 days and overall stocks across all types is 8.6 days, compared with 1.6 days for O negative and 4.3 for all types when the Amber Alert was triggered.

“However, with a shelf life of just 35 days, these blood stocks must be constantly replenished,” the spokesperson added.

To register to donate and to book an appointment, log on to blood.co.uk, use the GiveBloodNHS app, or call 0300 123 23 23.