Below are remedies if you have Low BP, BP drop upon standing. It would also help if you have POTS, but Low BP and BP drop upon standing are NOT symptoms of POTS. Licorice (Not DGL) would raise your BP if it is low. Not for long term (LT) usage.
Invest in legs compression sleeves that pump your blood upward. It could take up to 6 months for new blood vessels to grow which in turn would improve blood circulation. V-8 drinks are good to expand blood volume. There is no single remedy.
Finding the cause is important. From a Chinese medicine perspective, hypotension is a so-called deficiency pattern. The two key organs in the disease mechanism are the spleen and the kidneys. If the spleen is weak and empty, it is unable to transport ‘clear yang' upwards. As a result, too little Qi and Blood is produced. The kidney is the root of the spleen. Thus, a weak spleen will eventually also exhaust the kidneys. Herbal therapy and acupuncture helps support the spleen, stimulating the production and flow of Qi and Blood. Consult experienced TCM practitioner.
A few years ago, I was diagnosed with a condition called vasovagal syncope. To describe this condition as simply as I can (since most people have never heard of it), this condition causes episodes where you will pass out if not handled properly. Bascially, your body reacts to some kind of trigger which is unique to each person. Some have specific things such as needles, blood or other visual stimuli, others can be caused by stress, a rapid change in position/elevation, other stimuli, or (what I am "lucky" to have) no actual known trigger, so thus it happens pretty much whenever it wants. I noticed that this site doesn't have anything listed for this particular condition despite it being a surprisingly common condition. So I figured I would submit a few remedies I have found thanks to my doctor.
How "natural" this particular remedy is can be debatable, but it certainly helps. From what my doctor tried to explain, the ingredients in sports drinks like Gatorade, Powerade, or other sports drinks (organic products included), particularly high amounts of electrolytes, can help to try and prevent an episode from taking place. His recommendation was to drink at least 1 bottle (or 8 oz glass if you use a mix) a day and it does seem to help hold them off. Of course, it isn't fail-proof as there is no real way to completely prevent episodes from happening, but it will at least lower the chances of one happening.
Laying Down with Feet Elevated
This one isn't preventative, but more of "I'm having an episode and I would like to not pass out" and is the best possible treatment to do so. To understand how this particular remedy works, you need to have a better understanding of what this condition does to your body. After the event has been triggered, your heart slows down and your blood pressure drops. Because of this, blood stops being able to reach the brain. In order to get blood back to the brain, your head needs to be in a position in which blood can flow back to it. So, the only way your body knows how to make this happen is to make you pass out and fall to the ground, making your head level with your heart. As I'm sure you have already figured out, this isn't exactly safe and can lead to further problems (I've gotten a concussion or two from fainting during an episode - it's not fun in the least). In order to stop your body from getting to the point of fainting, the single best thing you can do is lie down and elevate your feet on some cushions, a chair, or anything else you can get to. This will naturally allow the blood to flow back into the brain and keep you conscious. At absolute minimum, this will ensure that if you do happen to black out, you're already on the ground and thus won't fall and hurt yourself.
I hope that both of these remedies may help someone else who suffers from vasovagal syncope to find some relief and potentially make episodes much less frequent and much safer.