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Even though you don't need to be a scuba diver to donate blood, most divers already know that donated blood can be a lifeline during emergency situations.
Usually, your body will replace the lost fluids within a few days. But, how long should you wait before you go scuba diving after donating blood?
There are a number of circumstances when scuba divers need to wait to dive, such as:
Blood donation affects the circulatory system, which generally results in less-than-ideal conditions for performing physical activities, such as breathing scuba underwater.
Most adults have at least five (5) litres of blood in their body. The amount of blood that most donors give during a donation is about 500mL (half of one litre). Thus, donors lose around 10% of their total blood volume during each donation.
Here's the thing:
According to the Divers Alert Network (DAN), the replacement of blood plasma takes about 24 hours and the body needs at least four (4) weeks to replace donated red blood cells.
Moreover, it can take eight (8) weeks for blood iron (protein) to return to pre-donation levels. Hence, even though a healthy blood volume returns a lot quicker, having a lower count of red blood cells usually results in dehydration and some lethargy or fatigue.
The Undersea and Hyperbaric Medical Society (based in Florida, USA) says these conditions increase a diver's risk of having a diving accident or decompression sickness (DCS).
Plus, the UHMS medical standards define the minimum waiting period for scuba diving after blood donation should be at least forty eight (48) hours. DAN is often more conservative and routinely recommends waiting seventy two (72) hours.
These are some of the primary reasons why scuba divers who give blood should wait the minimum period before going scuba diving:
To "err on the side of caution", and for the safety of yourself and the other divers in your group, the official safety guidelines are to wait at least 48 to 72 hours after a whole-blood donation before making a return to scuba diving.
This conservative waiting period allows the body to replenish a healthy blood volume and recover from the process of giving blood.
In some situations, the recommended waiting time for scuba diving after donating blood will depend on the type of donation that you made.
For example:
The Divers Alert Network (DAN) recommends waiting three (3) days after making a whole-blood donation (along with the majority of dive medicine experts).
Even though platelet or plasma donations (also called apheresis) return the red blood cells, there is still some issue with blood volume loss - albeit slightly less severe. Hence, a waiting period of at least one full day (24 hours) is generally advised.
As with many things in life, "listening" to your body has major benefits. It's best to return to diving only when you feel in general good health and completely back to normal. If there are signs of fatigue or lightheadedness - don't go diving!
Good hydration is one of the most important factors for all divers, and especially beginners. So, drink lots of water, along with other hydrating fluids, during the days leading up to the dive - and when the diving is finished.
Some scuba divers who donate their blood choose to take iron supplements. Unless your doctor advises against it, taking iron supplements can help the body speed up the process of replacing lost red blood cells.
It's best not to donate blood before a dive trip (such as multiday diving liveaboards). Instead, schedule your blood donations in advance of a planned diving excursion to allow adequate time for recovery.
Pro Tip: We always recommend discussing any medical status with a physician who is specialised in the most common scuba diving injuries or consulting the Divers Alert Network (DAN) for further advice.