"He has been flown to Dhaka and was taken to the Combined Military Hospital for a check-up.
He is expected to be released after 5:00 pm," the spokesman added.
Temperatures in Bangladesh have reached 41 degrees Celsius during a week-long heat wave, which is likely to continue until monsoon rains expected in the next few days bring relief.
At least 12 people have died of heatstroke in the past week.
Ahmed, a former central bank governor, took over as the head of Bangladesh's interim government after the country's president declared a state of emergency and cancelled polls in January.
He has vowed to carry out sweeping political, economic and electoral reforms before new polls are held in late 2008.