Way late for this reply but it might help someone else too. I've researched and experienced this first hand and noticed a pattern over the years.i kept a diary.
Yes it certainly does make you super tired. This is why: Prolactin that magical hormone that is responsible for so much. (Weight gain / stagnant weight loss, they don't tell you that when telling you breast is best do they?! I wasn't angry just bemused) you need prolactin to make milk it slows you both down, it makes you tired at the same time, makes your body aware you need to make milk and tells baby it's time to sleep, (sometimes they get the message but excitement keeps their little minds going!) it magical but unless you have an army of helpers you need to find away around the tiredness. It also tells you you need to sleep too, that lovely sleepy feeling you get when you out your head on the pillow that's prolactin, it's utterly magical but it's a task to juggle it. That's why we make more milk in the evenings and during the night because our prolactin levels are naturally higher. I made so much more milk at night than the day because of prolactin like do many other women notice too it's because of that magical hormone they fail to educate you about.
I had a routine of herbs throughout the day and doubled them at night ( juiced ginger, fennel seeds and hops... last one yuck!! )
It's the hormone that needs to be present in your body for your body to be aware that you need to make milk when baby/ babies are born, it's triggered by the suckling of your baby at birth etc. It's the trigger that tells your body ... baby here needs milk!
It's also responsible for the sleepy feeling you get at night ,( I know I'm repeating myself but I also know mummies skip read ,ðŸ¤) so you mix that with the Sleep deprivation, the stress of looking after you little one/s (your mind constantly running over jobs to do what baby needs etc) you've got a huge group of triggers that add to mental and physical exhaustion and the feeling of tiredness.
My help was :
vitamin d supplement (research it well because there are certain things that decrease milk supply mixed in with certain ones) daily exercise despite not feeling like it, timers etc that tell me to do things (feed cat, change washing over, write reports for work etc, I'm not kidding it keeps you on your toes and stops you forgetting things that adds to the stress and in teen makes you even more tired I added different tunes too for different things) and enjoying the sunshine with the kids that kept me going. Listening to music that was upbeat. I added a postnatal vitamin and breastfeeding supplements, I also ensured I took spa tone and stuck to a strict diet of 150g protein a day with lots and lots of veggies and fruit for pudding. I cut sugar out because I knew I'd struggle to loose weight despite my low calorie intake. Simply because the prolactin stops metabolism and stops your burning fat in its entirety. You will hit a sticking point with weight loss, so I helped it along with making myself eat really sensibly. Because I cut out sugar I stopped the energy dive. I however couldn't get rid of my morning coffee, I'm good but not that good, I'm still human 😸 I basically kept to my diet pre babies and added extra iron and protein to compensate for that used while feeding. I was combined breastfeeding of 12 years, my third was autistic and didn't want to stop nursing. I didn't mind, I have pretty thick skin after my upbringing and I could handle the funny looks 😉 we never made it obvious it just looked like lo was hiding under my top. I was always tired, always battling the tiredness but I stepped back realized I was raising the kids to be healthy, confident and happy and knew the tiredness was a small quibble even though at times I use to think I can't do this, I really can't do this!!!. I reminded myself they wanted it and I was responsible for them being born. I chose that my babies were in the world. I should be their comfort and support when they wanted it. I enjoyed breastfeeding very much because I knew it was a gift not for them but for me the time I had with them was special, it was a battle for me, the connection I had and have with my kids is phenomenal. I'm blessed with 4 children that are each confident and comfortable with the people they are. I can't honestly say that they wouldn't of been that way with formula I honestly think it's how you raise them not how you feed them, but my autistic child has certainly been positively affected by it. It's helped alot. I struggled with low supply but I found ways to increase it. I did consider domperidone but I gave the herbs a chance first and I'm glad I did. I used hops, juiced ginger (it's nasty but it works make sure you have a drink of juice afterwards ) and fennel. I led a simple diet because there were lots of things that were included in foods that harmed my supply like paprika and other things. I adored peppermint pre babies but obviously had to stay clear. I enjoyed chewing on fennel seeds for the sharp taste, I found I missed peppermint less with fennel seeds.
So yes is a quick way of answering it, it makes you tired for lots of reasons but it's mainly science.
I hope you enjoyed reading my journey it was exhausting living it but it was also something I'll be eternally grateful for.