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Navigating the Complexity of Fluctuating Capacity: Understanding the Mental Capacity Act

Updated: Sep 22, 2023


As practitioners tasked with assessing an individual's capacity, we often encounter complex situations that require a nuanced understanding of fluctuating capacity. The Mental Capacity Act (MCA) 2005 provides essential principles that guide us in making informed and respectful decisions in such circumstances. In this blog, we will explore the five key principles of the MCA and their application when faced with assessing someone with fluctuating capacity.

1. A presumption of capacity

The first and fundamental principle of the MCA is a presumption of capacity. This means that we should always assume that an individual has the capacity to make their own decisions unless proven otherwise through a formal capacity assessment. When dealing with fluctuating capacity, this principle reminds us that capacity can change over time. People may have capacity to make decisions at some moments and lack it at other times due to various factors such as health conditions, medication, or emotional state. It is vital to acknowledge this variability and approach each assessment with an open mind.

2 Individuals being supported to make their own decisions

The MCA emphasises the importance of providing support to individuals to make their own decisions whenever possible. This principle applies equally to those with fluctuating capacity. When assessing someone with fluctuating capacity, it is essential to identify the specific areas where support can enhance their decision-making ability. This support should be tailored to their unique needs and should enable them to participate actively in the decision-making process.

3. Unwise decisions

The third principle of the MCA states that an individual's capacity should not be questioned solely because they make unwise decisions. This is a crucial consideration when dealing with fluctuating capacity. Even if a person makes unwise decisions at times, it does not necessarily mean they lack capacity altogether. It is vital to distinguish between unwise choices and a lack of capacity, respecting their right to make decisions that might not align with what others consider as "wise."

4. Best interests

When an individual lacks capacity to make a specific decision at a given time, any decisions made on their behalf should be in their best interests. For individuals with fluctuating capacity, assessing their best interests becomes more intricate. It requires us to evaluate their capacity at the exact moment when the decision needs to be made and consider the relevant factors and information available at that time. Regular communication with the person, their loved ones, and other relevant parties can aid in understanding their evolving preferences and values.

5. Less restrictive option

The final principle of the MCA states that any decision made on behalf of an individual lacking capacity should be the least restrictive option while still achieving the desired outcome. In the context of fluctuating capacity, this principle urges us to carefully consider whether the person can be supported to make decisions themselves when they are capable of doing so. It also requires exploring alternatives to substitute decision-making, such as appointing a lasting power of attorney or seeking informal support from family and friends.


Assessing an individual with fluctuating capacity is undoubtedly a complex undertaking for practitioners. By adhering to the principles of the Mental Capacity Act, we can navigate these situations with sensitivity and respect for the individual's rights and autonomy. Presuming capacity, providing support, acknowledging unwise decisions, considering best interests, and exploring less restrictive options are the cornerstones of a person-centred approach to decision-making.

As practitioners, it is essential to continually educate ourselves about the complexities of fluctuating capacity and to maintain open communication with our clients, their loved ones, and other professionals involved in their care. By doing so, we can ensure that our decisions align with the principles of the MCA and promote the well-being and dignity of the individuals we serve.

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