If the maximum units of Botox one can get every 3 months is 400 units, can I still get more if the Botox is not working?

Thank you for your question.

The 400-unit limit every 3 months for Botox (onabotulinumtoxinA) is generally considered a guideline based on safety data from clinical trials and FDA approval. It’s not necessarily a strict, unbreakable rule — but rather a recommended maximum total dose to minimize the risk of side effects, such as antibody formation (which can lead to treatment resistance), systemic spread, or muscle weakness in distant areas.

In your case:
You’ve received:
200 units for the underarms (100 units each side)
200 units for the trapezius muscles
That totals 400 units — a high, but still within the typical safe range for therapeutic use.

If you’re still experiencing underarm sweating 3 weeks after injection, it may be due to:
Inadequate dose (some patients require a bit more than average)
Less-than-ideal injection technique or placement
Primary resistance (rare) or secondary resistance due to antibodies (less common but possible in high cumulative doses over time)
Other factors such as thyroid issues or medications that increase sweating

Regarding adding more:
It is sometimes clinically appropriate to administer a small touch-up dose if there’s been an inadequate response, particularly in focal areas like the underarms. A modest increase, such as 25 units per axilla, may be reasonable if you’re still symptomatic — but only under close supervision by your treating provider.

The 400-unit guideline is not absolutely set in stone, but exceeding it regularly may increase risks.

You should consult with your injector to evaluate why the initial treatment wasn’t fully effective.

A small supplemental dose might be considered safe if clinically indicated, but this should be individualized based on your health history and prior response to Botox.

I recommend a follow-up visit with your provider to assess your results and discuss whether a touch-up is appropriate.

If you haven't experienced relief from the Botox you've already received, you have to start asking yourself if an additional treatment with a small amount will make a difference. At this point, I recommend pursuing a discussion for other potentially more effective treatments for hyperhidrosis.