It's important to follow your doctor's advice, especially when it comes to prescribed dosages of supplements like folic acid. For chronic exhaustion and brain fog, there are some commonly considered supplements that might aid in improving energy levels and mental clarity, alongside maintaining a balanced diet and healthy lifestyle. Here are some supplements that could possibly support your situation:

1. B Vitamins: Beyond folic acid (B9), the full spectrum of B vitamins is often recommended for energy support and cognitive health¹. They play a crucial role in energy production and the synthesis of neurotransmitters, which can help with brain function.

2. Omega-3 Fatty Acids: Found in fish oil supplements, omega-3s are known for their role in brain health and reducing inflammation, potentially improving mental clarity and mood².

3. Coenzyme Q10 (CoQ10): This supplement is an antioxidant that can support energy production in cells and might reduce feelings of fatigue³.

4. Iron: Even if your iron levels are not specifically tested, fatigue can sometimes be related to low iron levels, especially in certain individuals like women of childbearing age⁴.

5. Magnesium: This mineral is important for many bodily functions and can help with fatigue and muscle relaxation⁵.

6. Adaptogens: Herbs like Rhodiola rosea and Ashwagandha are often used to help combat fatigue and stress, improving overall energy levels⁶.

Remember, it's critical to consult with a healthcare professional before starting any new supplement, especially if you have any health conditions or are taking other medications. They can help ensure that these supplements won't interact negatively with your prescribed treatments and are appropriate for your specific health needs.

If you're interested in exploring specific products for any of these supplements, let me know and I can help search for some options.