How much blood do fleas drink?


Adult cat fleas drink 6.97 ul of blood per day. Females eat more than males. They consume 13.6 ul of blood daily, a volume equivalent to over 15 times their body weight. Both sexes imbibe more blood than is digestible. The excess blood is excreted as feces to feed larvae.


Blood Consumption

Feeding Process

Fleas drink large amounts of blood, especially the females. As capillary feeders, they insert their mouths into a blood vessel. The host’s blood pressure gets exploited, which results in efficient feeding. To help draw blood, fleas have strong sucking muscles, as well as anticoagulant saliva. 24.9% of fleas complete a blood meal in 5 minutes, 97.2% finish within an hour Fig 1.


Fig 1 Percent of fleas (y-axis) that completed a blood meal across 80 minutes (x-axis).

Blood Consumed per Day

In a mixed gender study, cat fleas ingested 6.97 ul of blood per day. Females imbibe 13.6 ul of blood daily, which is equal to over 15 times their body weight. A kitten weighing one pound has 30 ml of blood. A heavy infestation, with 220 female cat fleas, could potentially consume 10% of the kitten’s blood per day and cause anemia.

Females vs Males

In five minutes, females consume over twice as much blood as males. By four hours, blood imbibed by females quadruples that of males. In an average feeding session, male fleas consume less than 15% of the blood volume of females. Males feed for 11 minutes, while female meals last 25 minutes. Males are more active on hosts, only remaining attached to feed for 10-20 minutes. Females, on the other hand, may stay in a feeding position for over three hours.

Weight & Size Increase

Adult fleas don’t molt. They only grow when their abdomens swell during feeding. Fully engorged fleas are double their unfed size and weight.

Males are smaller than females, with smaller abdomens. In an hour, females’ weight increases by 40%, while males only increase by 3%. By the 12 hour mark, females will add 75% to their weight. Cat fleas become fully engorged within 48 hours of feeding, with females increasing their weight by 140% and males by 19%.

Feces Production

Feces Excreted per Day

Cat fleas defecate large amounts of feces while feeding. Both genders imbibe more blood than they can use. The excess blood gets excreted, largely undigested. On average, fleas produce 0.645 to 0.770 mg of feces per day. Females excrete 17 times as much feces as males, 0.8546 vs 0.0503 mg daily.

Why Fleas Consume Excess Blood

Flea larvae require adult fecal blood (flea dirt) for food. Once an adult flea bites, imbibing and excreting excess blood has few energy costs. They may ingest excess blood to harvest out key nutrients, such as B vitamins. Or they may be purposely feeding larvae. Whatever the reason, the larvae greatly benefit in the end. It’s appears to be an evolutionary step towards parental care.


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