A very simple thought-experiment regarding the publicly acknowledged medicine stockpiling (which is entirely due to brexit) demonstrates that if you take six weeks of supply out of circulation to put into storage, you will have a shortage. That some pharmaceutical companies consider six weeks supply inadequate and are, therefore, stockpiling rather more, simply enhances that.Why drug shortages now all of a sudden? how very odd.
Some medicines are manufactured at only a few scheduled times - for two I know of, evidence suggests once a year. You can't simply ramp up production and make a few more to put to one side.
Having been involved in medicines from the point of view of patients for over ten years, I have seen problems come and go. I have never seen so many people having problems getting hold of the medicines they need. And that applies particularly to one of the most commonly prescribed long-term medicines - levothyroxine - for which demand is far easier to estimate than many others.
Certainly I acknowledge that other factors also affect supply. At this moment, I'd put brexit right up as the single most important factor.