There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Fidelity Select Health Care Services (FSHCX Quick QuoteFSHCX - Free Report) : 0.71% expense ratio and 0.52% management fee. FSHCX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy. FSHCX has achieved five-year annual returns of an astounding 14.36%.

Frost Growth Equity Institutional (FICEX Quick QuoteFICEX - Free Report) : 0.63% expense ratio and 0.5% management fee. FICEX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. FICEX, with annual returns of 11.17% over the last five years, is a well-diversified fund with a long track record of success.

Neuberger Berman Guardian Adviser (NBGUX Quick QuoteNBGUX - Free Report) . Expense ratio: 1.17%. Management fee: 0.88%. Five year annual return: 11.65%. NBGUX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.